BIO Midterm 3

Ecosystem components: Abiotic vs Biotic

-Abiotic components include: water quality, light availability, oxygen, substrate characteristics, temperature 1. Temperature: Low temperature limits the ranges of many animals and plants 2. Wind: Wind causes plants and animals to lose heat and water faster than they would in still air 3. Water Availability: Often limits the ranges of plants and animals (Only drought-adapted organisms can survive in desert habitats) 4. Water quality: Some plants and animals require only freshwater and some only salt water. Pollution degrades water quality and can also impact where organisms live 5. Light -In terrestrial habitats containing sufficient water, plants compete strongly for access to light -Light becomes a limiting factor in plant growth, but some are adapted to low light levels -In aquatic habitats light quality varies with water depth -Green algae only grow in relatively shallow water -Red algae can photosynthesize at greater depths 6. Salt: Soil as well as water can become too salty; Irrigated land becomes saltier over time as water evaporates but salt remains behind 7. pH (acidity): Different organisms are adapted to different pH in their environments, but most do best in a neutral environment - Acid rain has killed fish and trees in forests -The biotic components include: all living organisms present in the ecosystem (even microorganisms)

Trophic Relationships in Ecosystems KEY POINT: Energy moves in an ecosystem from the sun through the various trophic levels, decreasing with each transfer

-An ecosystem is a community of organisms living in an area plus the abiotic environment affecting that community -Ecosystem ecology is concerned with movement of energy and materials through organisms and their environments -Feeding relationships show how energy moves through the ecosystem -Food chain: a linear diagram showing what each organism eats and is eaten by -Food webs, or interconnected food chains, are more realistic representations -TROPHIC CATEGORIES AND RELATIONSHIPS: -Primary producers convert light energy into chemical energy and biomass through photosynthesis -Examples: algae, grass, seaweeds, crop plants, trees, weeds -Primary consumers or herbivores eat the producers, converting their molecules into chemicals and energy needed for the herbivore to grow and reproduce -Examples: zooplankton, grasshoppers, cows, rabbits, turtles -Secondary consumers or carnivores eat the primary consumers -Examples: bay anchovy and many other fishes, foxes, snakes, insect-eating birds -Tertiary consumers or top carnivores can eat secondary consumers -Examples: birds of prey, some fish, some insects -These trophic distinctions can be blurry in real life; animals will often eat a variety of foods -For example: squirrels are mainly herbivores, eating nuts and seeds, but careful study has shown that they will supplement their diets with bird eggs and nestlings if they can -Organisms which commonly feed at many different trophic levels are called omnivores -Besides these visible food chains, groups of organisms form detrital pathways -Detritus-feeders consume dead bodies and other organic wastes -Examples: earthworms, oysters, bacteria, fungi, crabs, sponges -There is a one-way flow of energy from the sun, to plants, then herbivores and carnivores -Only about 10% of the biomass of one trophic level can be converted to biomass of the next -The other 90% is converted to heat, the least useful form of energy -Invertebrates and microorganisms are more efficient in their use of food energy than vertebrates -Inefficient transfer of energy between trophic levels explains why producers are present in the largest numbers, and there are fewer herbivores, still fewer carnivores, etc. -trophic pyramids express numbers, biomass or energy of each trophic level -Pyramids of numbers are usually biggest at the bottom -But they can sometimes be inverted -Pyramids of biomass are also usually bottom heavy with a large producer biomass -But they can also be inverted in certain circumstances, usually in aquatic ecosystems -when the levels are expressed in terms of the energy that they contain, the pyramid is always upright -As energy moves along the food web, so do other molecules which don't break down -From producers they get into the primary consumers and then to secondary consumers -This is called biomagnification, and is often seen in toxins -One of the best known examples of biomagnification is the pesticide DDT, which caused drastic declines in bird species before it was banned in the US -If a small amount of DDT is applied to a waterway to control mosquitoes, the plankton in the waterway each take up a bit -The fish eating the cells get a small dose from each one -they consume and build up a higher level of toxin -The bigger fish eating those little fish get all of the DDT the little fish has consumed in one bite -Then the fish-eating birds get a huge dose of DDT with each fish they eat, representing all of the DDT on all of the algae supporting the growth of all those smaller fish

Community Biodiversity

-Biodiversity refers to the many different species of organisms making up a community and also to diversity in higher groupings -Biodiversity has several aspects -richness: number of different representatives of a group -evenness: the relative abundance of the group -ecologists calculate biodiversity indices that incorporate richness and evenness of species -MANY FACTORS INFLUENCE COMMUNITY BIODIVERSITY: -Latitude: species increase from the poles to the tropics -Topographic variation increases species richness since it provides more variable habitats -Peninsular effect: species richness decreases with increasing distance from main body of land -Hypotheses to explain latitudinal gradient -Time: communities diversify as time goes on, since evolution of new mutations, subpopulations, and species all require time -Places that were glaciated during the Ice Ages have fewer species since they have had less time to evolve new species after glaciers killed off most of the community -supported by a comparison of the more diverse fauna of an unglaciated lake, Lake Baikal, with a similar size lake at similar latitude that was covered by glaciers, Great Slave Lake -Area: larger areas contain more species because they have more diversity of habitats -Supported by some experimental evidence -However, demonstrably not true in many cases -the open ocean is the largest area on Earth but it has much less diversity than near shore waters -Tundra is the largest terrestrial biome but it has much less diversity than most other biomes -increasing heterogeneity: =more different types of habitats and ways of making a living are available -Productivity: areas with more plant producers have a larger base to the ecosystem and therefore can support more diversity -Disturbance: greatest species diversity is seen in communities with intermediate levels of disturbance -Disturbed areas include those impacted by natural disasters or high levels of predation, parasitism or herbivory -r-selected species prefer highly disturbed areas and k-selected species prefer areas of low disturbance; intermediate level of disturbance would include both -Even within diverse communities like coral reefs and tropical rain forests, those with moderate disturbance have higher species richness than those that are undisturbed or severely disturbed -predators, pathogens and parasites target the most numerous species

Biodiversity KEY POINT: There are many ways that humans rely on the natural world and suffer as it deteriorates.

-Biodiversity stabilizes ecosystems by allowing more complex feeding relationships -Allows species to survive by helping one another, for example desert palms provide habitat for many species that otherwise would not survive in the desert -Biodiversity is an increasingly important issue; Currently, the Earth is suffering a loss of biodiversity as many species become extinct -In true extinction an entire lineage is lost, with no living descendants (Example: trilobites) -In pseudoextinction one species evolves into another, maintaining the line, but the parent species dies out (Example: horses, horsetails) WHY IS IT IMPORTANT FOR PEOPLE TO MAINTAIN BIODIVERSITY? - new products and drugs to be discovered among the millions of uncatalogued species -little genetic diversity in most of our crop plants -we need to maintain their wild relatives as sources of genes that could be added to cultivated varieties if needed -Philosophical considerations -species have an intrinsic right to exist -important symbols and sources of inspiration to people -environmental thinkers argue that to lose species has an impact greater than the possible loss of products; that it diminishes humanity to exist in a diminished and impoverished natural world -The ecosystem as a whole provides services for humans -- "ecosystem services" include -plants and bacteria remove toxins and particulates from dirty air and water (bioremediation) -plants stabilize land which otherwise might slide, damaging homes and property -birds and bats remove tons of annoying and damaging insects from fields, forests, and yards -bees pollinate crops; without them fruit and many vegetable crops do poorly or fail altogether -flood control and water management

Kingdom Animalia: the animals KEY POINT: Animal groups added new traits to the previous ones as they evolved, and modified old traits to make them better adaptations.

-Characteristics: no cell walls, can usually move, ingest their food -Development includes blastula stage -Animals appeared suddenly in a burst of evolution called the Cambrian Explosion -Major living animal = phyla SPONGES: -the most primitive animals -no real tissues or organs, non-motile, asymmetrical -Defend themselves like plants, with sharp thorns and toxins -Filter feeders with water canals running through their bodies CNIDARIANS: -jellyfish, hydra, corals, sea anemones somewhat more advanced -cells organized into 2 tissue layers, making a more complex body possible -defend themselves and capture prey with stinging tentacles - Corals are very important in ocean ecosystems and productivity -radially symmetrical -- float around randomly so no direction is more important than another or don't move much -Primitive incomplete digestive systems with only a single opening, only one meal can be digested at a time FLATWORMS: -Flatworms like planaria are much more advanced, forming true, although primitive, tissues and organs -the first to develop bilateral symmetry, as seen in most of the higher animals -bilateral symmetry and forward movement in space resulted in evolution of a brain and head -led to cephalization -Most exchanges with the environment occur through diffusion -Flatworms include dangerous and damaging flukes and tapeworms ROUNDWORMS: -extremely small, abundant, unsegmented worms -Free-living or parasitic -first to evolve a complete digestive system with both a mouth and anus -allows continuous feeding and the specialization of regions within the digestive system -greatly increased the rate and efficiency of feeding, allowing the animal to take in much more energy MOLLUSCS: -diverse group, most with shells, including clams, snails, and squids -very successful; found in many habitats -demonstrate a new evolutionary adaptation, the coelom -a space inside the body filled with fluid, between the gut and the body wall or muscles -A coelom allows greater flexibility of the body and more space for internal organs -often used as a hydrostatic (water-based) skeleton for animals lacking hard parts ANNELIDS: -include earthworms, leeches and many fantastic-looking marine worms -segmentation is an innovation first seen in the annelids body sections were repeated, allowing the animal to grow bigger without needing new parts Segmentation is a good way to make the animal bigger without needing new genetic information ANTRHOPODS: -the most numerous and successful animal group -include crabs, spiders, ticks, scorpions, centipedes and insects -arthropod characteristics include jointed legs and a hard exoskeleton -Very mobile with their legs and thin exoskeleton -Also segmented, and evolution has specialized segments for different jobs, making them more efficient than annelids ECHINODERMS: -interesting, unusual animals -radially symmetrical like some of the very primitive phyla, but much more complex and mobile -completely unique characteristic, the water vascular system. -Water flows through their bodies in a series of canals, and is responsible for most body functions, including movement, which is based on a myriad of tiny tube feet -Well-known echinoderms include sea stars, brittle stars, sea urchins and sand dollars VERTEBRATES: -the most complex animals, including sharks and rays, bony fishes (the most numerous group), amphibians, reptiles, birds and mammals -vertebrates, like the other groups, evolved in the water, and the fish were the first -most primitive are the lampreys -sharks and rays are the next group; they form cartilage only, and have no bones -Very good senses, great predators but not buoyant and can't stop swimming -fishes have by far the most species of any vertebrate group -an important evolutionary innovation in the bony fish was the swim bladder -allows fish to control their depth without constant swimming, and would go on to evolve into lungs -lobe-finned fishes gave rise to the amphibians, the first vertebrates that could live on land -only semi-terrestrial AMPHIBIANS: -Amphibians have soft moist skin which can dry out most cannot reproduce on land, because their eggs are not waterproof -They return to the water to lay their eggs and for early larval development -after evolution of the amphibians, the world became colder and drier -amphibians were not well adapted to this and reptiles evolved from them REPTILES: -fully terrestrial with dry, scaly skin and hard-shelled eggs which can survive in the air -Internal fertilization was required since the egg was waterproof -some of the best known reptiles were the dinosaurs, which are extinct, but their line remains with us in the form of birds, the next major animal group BIRDS: -evolved from feathered dinosaurs; their claim to fame is the ability to fly -modifications throughout the body including bones and gonads lighten it to support flight -warm-blooded MAMMALS: -finally, mammals evolved from another group of reptiles warm-blooded, have hair, and form milk to feed their offspring

human populations KEY POINT: Human population growth must become logistic and resource distribution must become fairer if our species is to survive.

-Demography is the study of the size and rates of change of human populations (based on census data) -Percentage of humans who have ever lived who are alive now=6.5% -It is unclear how similar human population growth is to that of other organisms, and to what degree the same constraints hold -Currently, the human population is growing exponentially -The overall human population growth is about 1.2% per year, down from a high of 2.1% in the 1960's -The doubling time is currently about 61 years -For anyone over 61 years old, there are more than twice as many people on the Earth now as there were when they were born -For an exponentially growing population to remain healthy and happy, its food supply must increase exponentially as well -2 ways to keep the rate of exponential growth down: (1) Reduce the birth rate...delayed marriage, availability of birth control, women's rights, and small family policies as in China -Female literacy and economic and social power are highly correlated with reduced birth rates -Woman often want fewer children but cannot enforce their wishes if they are powerless, illiterate, and lacking in skills (2) Increase the death rate...Methods include famine, war, disease plagues, crime -In wild populations, both occur when overpopulation becomes a problem -Most people agree that the Earth has a carrying capacity for humans which will, one way or another, limit human population growth -Our population growth must switch from exponential to logistic at some point -No one knows what the carrying capacity is -Unlike the situation with other animals, human carrying capacity varies with advances in technology -Some people, for example the late economist Julian Simon, dispute the concept of a limiting carrying capacity as applied to humans -When other species of plants or animals overshoot their carrying capacity, the normal result is a population crash -Sometimes the environment becomes so damaged by the excess population that the carrying capacity itself is decreased during the overshoot -Some environmentalists worry that we are have already overshot the Earth's carrying capacity and are in the process of permanently ruining the environment HUMAN POPULATION ESTIMATES: -if human population growth becomes logistic, population estimates for the year 2150 range from 4.3 billion to 28 billion -If growth remains exponential, the estimate is 296 billion Numbers aren't the only important indicator of a human population's use of resources -Some people use many more resources than others -A significant contributor to world instability is the fact that people in the developed world use many times more resources than people in the developing world -If everyone lived at the same consumption level as the average American, we would need 4-5 Earths to feed, house, and supply everyone DEMOGRAPHIC TRANSITION: -a predictable series of changes occurring when human societies become more technologically advanced -STAGE 1: population size low but stable due to high birth and death rates -Many births are needed to maintain population size in the face of high losses due to disease, injury, etc. STAGE 2: technological advances lower the death rate but birth rate remains high due to social and familial expectations -This results in rapid, exponential population growth STAGE 3: population growth becomes logistic as birth rates decline. -The population adapts to the lowered death rates and realizes that fewer babies are needed STAGE 4: the population achieves zero population growth as, on average, each set of parents has only 2 children to replace themselves -The age structure of a population shows at a glance what sort of population growth to expect -Fast-growing populations have wide-bottomed age pyramids, while stable populations have pyramids with nearly vertical sides -When the bottom of the pyramid is wider than the middle, large numbers of people will be entering their child-bearing years in the future, and the population will continue to increase -When the middle of the pyramid is widest, more people will be moving into middle and old age than into child-bearing years and population growth will stabilize -Life expectancy varies with the degree of technology available to a culture -A child born into any country has a life expectancy based on how long others of the same gender survive in that country, which in turn is based largely on medical care available, whether famine and wars are problems, and effective control of infectious diseases -Technologically advanced countries have life expectancies in the 70's and 80's, while some developing nations have life expectancies below 50 years

Community ecology

-Ecological communities are the group of populations living together in the same habitat -wide variety of scales, from a large forest to a small pond within the forest - Ecologists study how communities are structured, why each community consists of its unique set of species, and how communities change over time HOW DO COMMUNITIES WORK? -Organismal model: groups of species work together like organs of a body, and are consistently found together -predicts that communities have sharp boundaries -Individualistic model: species in the community coexist because they need similar environmental conditions -Communities would not have sharp boundaries but consist of populations that change independently of one another - Experimental evidence supports the principle of species individuality -Each species is distributed according to its own physiological needs and population dynamics -Communities usually merge gradually from one to another without sharp boundaries -Occasionally sharp boundaries between communities are seen, usually because there is an underlying sharp boundary in the environment

Productivity

-Ecosystem Productivity : varies based on energy coming in, nutrient availability, and climate -Gross primary productivity: total energy taken in by an ecosystem, including that used for metabolism of producers -Net primary productivity: energy not used for metabolism but stored as increased biomass, available for growth, reproduction, and use by other organisms -Primary productivity in terrestrial ecosystems is determined by water and nutrient availability and by temperature -The nutrient in the shortest supply in an ecosystem is the limiting factor; when it is added plants will respond with faster growth -In aquatic ecosystems, primary productivity is determined by light and nutrient availability -highly productive ecosystems include rain forest and estuaries; tundra and open ocean are low productivity ecosystems -Biogeochemical cycling: Atoms of mineral elements move between the soil, air, plants, and animals -Minerals in plants are eaten by animals, form the animals' bodies, and then return to the soil through wastes and decomposition of the animal after it dies -minerals can be temporarily lost when bodies of plants or animals become incorporated into rock -agriculture disrupts mineral cycling -most soil nutrients end up in treated wastewater and are released into aquatic environments -resulting in the need for fertilizers on land, and eutrophication of aquatic ecosystems -Commercial plant food, or fertilizer, normally contains nitrogen, phosphate, and potassium, the nutrients most likely to be low in soils -Organic fertilizers include compost, animal (or human) waste, and leguminous crops (green manure) -Inorganic fertilizers: chemicals added to the soil; more expensive and are readily available to the plants or to be washed away if not used up fast enough

hominins

-Hominins are humans and our close relatives and ancestors -Bipedalism, the ability to walk on two legs, is the defining character -Allowed faster movement over longer distances and freed the hands for tool use or carrying -Allowed parents to carry babies -Another hominin evolutionary trend is decreased size and strength of jaws and teeth -Apes have only their teeth for cutting, scraping and chewing; hominins use tools -Increased brain size, enhancing the ability to plan, make tools, and communicate, eventually to speak -Differences in the throat and larynx allow humans to speak while apes cannot, but they can learn sign language -Apes have the intellectual capacity for conversation, but lack the physical means -Apes show rudimentary tool use and culture -Chimpanzee groups fish for termites with sticks, but different groups prepare their sticks differently, and mothers or other mentors pass on the practice to the young -Some monkey groups have learned to wash their food before eating -Among humans and apes, social success equals fitness, because individuals with greater social skills are more likely to survive and raise successful offspring -Jane Goodall carried out groundbreaking studies on the importance of parenting in producing socially successful offspring -The study of hominin evolution has become more complicated recently as new finds cast doubt on earlier ideas about human origins -The scarcity of fossils originally led people to think that the human family tree had just one branch -It now seems more likely that there was a bushy human family tree with many species evolving from one or more bipedal African apes -with several lines that became intelligent and used tools, all eventually becoming extinct except us

human traits KEY POINT: Humans represent one end point of an unbroken line of evolution starting from the first living cells on Earth.

-Human history, like that of all living things, goes back to the beginning of life on Earth -Human genes and traits evolved over billions of years from genes in the first bacteria-like cells -We share traits with all other cells on Earth -All cells use the same molecules in the same way -Billions of years after those first cells evolved, animals had a common ancestor -As the ancestral species evolved it passed on common animal traits, including ingestion of food, cells without walls, and similar developmental patterns -For example, humans and jellyfish have similarities in the genes determining body patterns -Later, the vertebrates had a common ancestor descendants inherited skeletal structure, body plan and organs -About 3/4 of human genes have similar counterparts in the pufferfish genome -Around 225 million years ago, the first mammals evolved After dinosaurs became extinct, mammals diverged into many different types -This was an adaptive radiation made possible by the availability of resources previously used by dinosaurs -The descendants of the first mammals, including us, retain many of their genes and features -About 90% of the mouse genome is similar to parts of the human genome -As mammals took over many different habitats, one kind started to live in trees -It began the primate line, to which we belong PRIMATES: -appeared around 60 million years ago -Human adaptations were derived from primate traits -As evolution proceeded, we modified these traits for new environments and life styles -Primate adaptations to living in trees -hands and feet with nails rather than claws -Hands and often feet with opposable thumbs for grasping -Later, the hands could be used for carrying and manipulating objects -Very mobile shoulders permits a huge range of movement of the arms -Apes swing hand over hand in trees; humans can manipulate arms with great precision, for example in gymnastics and tennis -Forward facing eyes allow depth perception -essential for swinging and leaping from branch to branch -Primates rely mainly on vision rather than olfaction (smell) to understand their environment -Depth perception required reshaping the face for stereoscopic (both eyes forward) vision, impossible with a large snout -highly developed nervous systems and large brains visual center of brain is large; complex 3-dimensional structure of trees requires quick and accurate processing of large amounts of information -Large brains led to complex social interactions and eventually tools and technology -There are currently about 200 species of primates on Earth -Many are at high risk of extinction -Prosimians (pre-monkeys): tarsiers, bush babies, small insect-eating tree dwellers, are the smallest and most primitive -New World monkeys: howler monkeys, capuchins have prehensile [grasping] tails, flat noses, live in trees -Old World monkeys: baboons, rhesus monkeys have non-prehensile tails, protruding noses, live in trees and on the ground -From the old world monkeys the hominids, or ape line, branched off

Species Diversity and community stability

-Important to study and measure; instability may indicate an ecological problem -Loss of bird species led to understanding the problems with DDT -Diversity-Stability hypothesis: more diverse communities are thought to be more stable -Disturbances in a species-rich community would be cushioned by large numbers of interacting species - Dr. Tilman studied grass plots for 11 years, found that greater species richness was associated with greater biomass production and less year to year variation -He hypothesized that communities that had both disturbance-sensitive and disturbance-resistant species would react better to disturbance -- the resistant species increasing their abundance when the sensitive species were reduced -The graph shows a correlation between species richness in grass plots and a measure of year-to-year variability in biomass. The plots with greater species richness had less variability; their biomass was more stable over time.

Modern human populations and races

-Like other organisms, humans adapt to their environments through the process of microevolution -Several factors determine the adaptiveness of skin color, including production of vitamins D and folate, and protection from skin cancer -These explain the observation that natural populations of people living nearer the poles are lighter-skinned and people living nearer the equator are darker-skinned -The relationship is really between UV light levels and skin color -Folic acid is a vitamin required for proper embryonic development and for normal sperm count -UV light penetrating the skin destroys folate in the body, making it hard to maintain levels required for reproduction Individuals who blocked UV light into the skin had an advantage over those who did not, and dark skin was selected for where UV light was intense -All humans, evolving in Africa, must have started out with dark skin -So why did that change? -Vitamin D is produced in the skin when UV light penetrates -Vitamin D is needed for bone development -its lack causes rickets in which bones fail to develop properly, leading to weakness and crippling -Women with low vitamin D may have more difficulty with the birth process than others -Pale skin is an adaptation to maximize the body's ability to synthesize vitamin D under low UV conditions -As people migrated out of Africa, they accumulated mutations decreasing skin pigmentation so they could get as much vitamin D as possible from their limited sun exposure during cold Northern winters -In addition, dietary habits and customs such as exercising outdoors in winter contribute to the ability of pale-skinned Northern people to get enough vitamin D -Each population maximizes its fitness by evolving a skin color that maintains folic acid and makes enough vitamin D -Eskimos or Inuit people are an exception to the north = light rule -They are not pale because they do not get their vitamin D from the sun, but from fish liver, an extremely rich dietary source -Cultural evolution: fish liver is a delicacy shared by all -Nose shape is another human variation related to natural selection -Long, narrow noses are favored in dry environments, because they help moisturize air before it reaches the lungs -Flat noses are seen in people from warm, humid environments, because the air does not need to be moisturized

Plant food

-Mineral elements in the soil that plants need -Plants get carbon from air, but their molecules also contain other elements like nitrogen, phosphorus, iron, etc. -These are obtained by roots from the soil -Different soils have different amounts and types of mineral nutrients available in them -Nitrogen is often the most limiting soil nutrient -easily lost from the soil -needed in many cellular molecules -There is plenty of nitrogen on Earth -Most of it is in the form of atmospheric N2, which is not available to plants -This free nitrogen must be "fixed" (made into organic form) before it can be used -Nitrogen can be fixed by -Lightning -Industrial processes -Nitrogen-fixing bacteria -Some plants are adapted to living in nitrogen-poor soils, including the carnivorous plants -They produce various types of traps to capture animals -usually insects, but sometimes small vertebrates as well can be trapped inside large pitcher plants -this giant montane pitcher plant is designed to capture and digest tree shrew poo -The animals or their products are digested by the plant and used as a nitrogen source, not as a source of energy to grow

Photosynthesis

-Most important set of biological reactions occurring on Earth -Provides all biological molecules, all energy, and all oxygen used by animals -Plants are autotrophs, producing their own cellular molecules from basic raw materials -They also provide molecules needed by heterotrophs, which are animals, fungi, etc. -Chemical reaction for photosynthesis: 6CO2 + 6 H2O → C6H12O6 + 6O2 -This is the opposite of the reaction for aerobic respiration Plants and animals each supply what the other needs -Photosynthesis is divided into two big parts 1) light reactions 2) dark (or light-independent) reactions -Both occur in plants' green chloroplasts -Light reactions: -Begin when light is absorbed by one of the photosynthetic pigments -Each pigment absorbs light at specific wavelengths, and contributes that energy to photosynthesis -Light energy goes through reactions in the chloroplast converting it to cellular energy compounds ATP and NADPH -These cycle between non-energized forms ADP and NADP+ and energized forms, ATP and NADPH -As a side effect, water is split apart to produce oxygen -Summary for light reactions: Light energy is transformed into chemical energy of ATP and NADPH; Oxygen is a waste product -Dark reactions or Calvin cycle: ATP and NADPH made during light reactions are used to convert carbon dioxide from the air into glucose -The glucose provides energy to the plant cells and building materials that the plant uses to grow -If the glucose is not needed immediately, it is further stored as starch

How are plants adapted to their environments? Key Point: Plants have two types of vascular (transport) tissues: xylem for water and phloem for sugar.

-Most leaves are adapted to be solar collectors that carry out photosynthesis -Flat shape: maximizes solar collecting surface -Internal structure: The top layer of photosynthetic cells have columnar shapes -They absorb some light and channel the rest to the lower cells -Lower cells have irregular shapes, bouncing light around inside the leaf rather than channeling it out -Stomates: allow gas exchange for photosynthesis (carbon dioxide in and oxygen out), but can be closed by guard cells to prevent excess water loss -Leaves can be changed by evolution to carry out other roles -Storage leaves store food, for example the thick leaves of onion bulbs -Reproductive leaves such air plant and walking fern produce clones of the parent -Pitcher leaves and trap leaves of carnivorous plants capture animals -Roots: underground miners for water and minerals -Root adaptations: Long, thin shape squeezes into cracks and maximizes surface area, where water and minerals are taken up -Root hairs are extensions of the epidermis which increase surface area more -The root cap secretes slime to ease movement of the root through soil -Root caps are also sense organs, telling the plant which way is down (sensing gravity) -Roots can be changed by evolution to be modified for different roles -Storage roots store nutrients (example: yams, carrots) -Aerating roots: "knees" of cypress trees are roots which grow up out of the water allowing oxygen to diffuse into the root system -Prop or buttress roots help a plant remain standing even in high winds or soggy soil -Stems: Connect roots and leaves, Adapted for transport of materials -Water moves from the roots up the stem to the leaves in the xylem -There is no pump; water moves due to a concentration gradient -There is more water in the roots and less in the leaves, from which it is constantly evaporating -Xylem cells are adapted to moving large amounts of water fast, They are dead and hollow -Some have no end walls and are stacked one on another like sections of pipe -Water has several roles in the plant: needed in photosynthesis; gives herbaceous plants most of their strength -Water pressing on strong cell walls allow the plant to stand up - the plant is 'turgid' -Sugars move through the stem in the phloem, from leaves to roots, storage organs, and buds -Unlike water movement in the phloem, sugars can go in any direction, even from storage organs to leaves -Stems can be changed by evolution to be modified for different roles (ex: Cacti have green, photosynthetic stems) -Leaves have been modified into spines to ward off predators and dissipate heat, so the stem has taken over the photosynthetic function -Storage stems: potatoes are actually underground stems which store nutrients as starch -Potatoes are stems, not roots, because they have external buds (eyes) and roots don't form buds

population size KEY POINT: Populations are studied in terms of their spatial distributions, sizes, and life history, and growth characteristics.

-Population size varies over time, going through predictable stages 1. Growth: the population gains members faster than it loses them -Resources are plentiful in comparison to the size of the population and reproduction is rapid 2. Crash: if the population grows too rapidly, it may outstrip resources, resulting in an imbalance between population size and resource availability that is balanced by the crash 3. Stability: the population size remains approximately constant -Population size and the resource availability are approximately balanced -Longest phase for most species 4. Decline, when the population loses members faster than it gains them -Could be due to factors including climate change, evolution or immigration of a new competitor or predator, disease, etc. 5. Extinction -Most populations end in extinction -Over 99% of all species that ever lived on Earth are now extinct -To understand population size changes, we need to know the ins and outs -birth rate -death rate -immigration rate (migration in) -emigration rate (migration out) -From these, the growth rate, r, can be calculated easily: r=birth rate-death rate+immigration rate-emigration rate -These are all rates, that is, proportions of the population -Raw numbers are meaningless -For example, country A had 589,653 new babies last year and country B had 887,074 new babies last year -We can't compare how populations are changing until we find out that the birth rate in country A is 4%, while that in country B was 0.4% -Now we can see that the population in country A is growing much more rapidly than that in country B

FOSSIL HOMININS Note: Evolution is not a finished event, of which we, humans, are the final product. It is a continuing process which has been changing and forming life on earth for billions of years and will continue to do so as long as organisms are born, die, and compete for what they need to survive and reproduce.

-Sahelanthropus tchadensis is a very early hominin, dated at 7 million years old -An early probable hominin fossil is the 6 million year old Orrorin tugenensis fossil discovered in 2001 in Kenya -Chimp sized with apelike arms and hands but bipedal -May have been a direct human ancestor -Ardipithicus ramidus, discovered in 1992, also had chimp-like characteristics and was probably bipedal -Lived 4-5 million years ago; its place in the human family tree is unknown -Australopithicus afarensis or "Lucy" was thought to be a primitive direct human ancestor, but new discoveries have made this seem less likely -one of the best known human relatives due to the abundance and completeness of its fossils -afarensis was bipedal as shown by pelvis and knees, and by fossilized footprints showing individuals walking on two legs -The pattern of weight distribution in these footprints is the same as in bipedal organisms, not like chimps who normally walk on 4 legs -Bone and facial structure were between human and chimp -A. afarensis lived throughout East Africa from 2.5 to 4 million years ago -Australopithicus africanus evolved later; they were taller and more human-looking, lived 2.5 to 3 million years ago -The face was less jutting than afarensis, but its body had apelike proportions with long arms and short legs -Australopithecus garhi dated 2.5 million years ago may be a link between Australopithecus and Homo -Authorities disagree about how many different species of Homo there were, and the relationships between them Area of active research -Homo habilis (Africa, 2.5 to 1.8 mya) is thought by some to be the most primitive member of the genus Homo -Originally thought to be the first to make simple stone tools -They had larger brains, flatter faces, smaller teeth, and more human hands then the Australopithicines -It believed that they could speak and we know they lived in social groups -Homo erectus was a later, more advanced human relative Some believe it evolved from H. habilis and some do not - we will go with yes -H. erectus had a much bigger brain, used fire, and migrated out of Africa -Fossils have been found in the Middle East and southern Asia; they did not seem to cross water -Another fossil species, H. ergaster, is often considered a variant of H. erectus that only lived in Africa -More advanced tools, a striding gait, lived 1.5 million to 300,000 years ago -They seem not to have been on the direct line of evolution to our species -Homo habilis may have produced archaic humans or Homo heidelbergensis, on the direct line of evolution to Homo sapiens -These people spread through Africa, the Middle East, and into Europe -More human looking, bigger brains, still with heavy brow ridges, receding chins and foreheads -Made spears and axes, and hunted large game -From H. heidelbergensis came 2 additional species: Homo neanderthalensis, or Neanderthal man, and Homo sapiens -H. neanderthalensis lived 250,000 - 30,000 years ago, and co-existed with H. sapiens for many thousands of years -Short, stocky and muscular, adapted for cold climates -Lived in Europe and the Middle East -Good hunters, made many tools -Believed to have spoken and to have had extensive culture, including burials, beads, and cave paintings -They died out and it is controversial whether any of their unique genes are found in modern humans -A combination of increasing glaciation and competition from H. sapiens may have led to their extinctionHomo sapiens appeared in Africa from Homo heidelbergensis about 130,000 years ago -We have the smallest faces, with a very small jaw pushed underneath the skull, and big brains -From Africa, H. sapiens migrated throughout the world and emerged as the only representative of the genus Homo

Flowers form the 4 reproductive organs of the angiosperm

-Sepals protect the flower in the bud -Petals may have colors, odors and/or nectar to attract animals -Stamens form pollen, which will produce the sperm -The carpel is the female part of the plant: pollen lands on the stigma at the top of the carpel -eggs are formed inside ovules in the ovary at the bottom -Flowers are adapted to attract pollinators, or to use the wind to transfer pollen -Flowers using specific types of pollinators have recognizable characteristics -Bee flowers are blue or yellow, sweet smelling, large and sturdy -provide nectar and/or edible pollen -often have special markings showing where the nectar is located -Bat flowers are large, sturdy, open at night, pale colored, often strongly scented -Butterfly flowers are large, with a place to stand but often delicate, provide nectar down a tube into which the butterfly sticks its tongue -The location of the nectar is often marked with little arrows to make it easier to find -Hummingbird flowers are bright red with a long tube, often with protruding stamens to dust the bird with pollen, lots of rich nectar, no odor -Some flowers trick their pollinators and get pollinated without providing a reward, like these wasp flowers -Fly flowers smell like rotting flesh to attract flies -Wind pollinated flowers have no or small petals, no scent, no nectar, fine dry pollen and large sticky stigmas -These are the plants responsible for allergies, because their pollen flies through the air -Trees and grasses are responsible for most pollen allergies -fruits develop from flowers -Transfer of pollen from the stamen to the carpel is pollination -After pollination, the pollen germinates and a tube grows to the ovary -Chemical signals help the pollen tube find the ovary -When it reaches the ovary, the pollen tube releases sperm to fertilize the egg -After pollination, the sepals, petals, and stamens are lost -The ovary wall develops into the fruit and the ovules within the ovary form the seeds

Niche

-Species inhabit biomes, ecosystems, and habitats, and share them with many other species as well -But each species has its own unique niche within its habitat, defined by its specific relationships with all components of the habitat -A niche includes an organism's limits of temperature, moisture, food, space, pH, salinity, and any other factor you can think of -Some organisms are generalists and have large niches; they can tolerate a wide range of conditions -Specialists, on the other hand, have limited tolerance to variable conditions but are very well adapted to their specialized niche -Fundamental niche: all of the conditions under which a species could live - based on abiotic factors -Realized niche: narrower, includes only where the species is actually found - based on competition, and therefore, biotic factors -Each habitat contains many distinct, but overlapping niches several bird species live in the same trees and eat insects, but each specializes in a different type of insect or part of the tree -tree is the fundamental niche -species subdivide the tree into different realized niches as each utilizes a particular type of hunting behavior -Symbioses are intimate associations between one species and another -Relationships between species are a central part of each species' niche -predation/parasitism/herbivory: one species benefits at the expense of the other by feeding off of it -examples: coyotes and rabbits, parasitic worms, parasitic plants such as dodder or Indian pipes, disease-causing bacteria -a graph of predator and prey populations often shows alternating highs and lows as each population affects the other. -co-evolution between parasite and host can result in increased tolerance of the parasite by the host, since death of the host is inconvenient or fatal to the parasite -Antipredator defenses and responses: predators and prey go through an evolutionary 'arms race' as each tries to out-evolve the other -Chemical defenses are toxic, irritating or bad tasting chemicals -Physical defenses include appearance and weaponry like spines, quills, claws, teeth -Reproductive defenses attempt to produce more offspring than are taken by predators -Parasitism is a popular lifestyle among all types of organisms - up to 4X -more parasites than free-living species -Many different types, sizes, strategies -Parasites often alter the behavior of their hosts to enhance transmission to new hosts -Newly introduced parasites can be very damaging and have nearly wiped out American elms and chestnuts, among others

Population control

-To manage ecosystems, we need to know whether populations are controlled in a bottom-up or top-down manner -Bottom-up means that populations are controlled largely by the amount of plant material available as food -Often assumed to be true -A related idea is that populations are controlled by the amount of nitrogen they have access to, because plant material is usually low in nitrogen but animals need a lot -These hypotheses predict that either increasing the total biomass of plants, or increasing the nitrogen in the plant food, would result in greater herbivore populations -Only nitrogen has experimental support -Top-down regulation means that predators control populations of prey which in turn control plant populations -Many experiments and observations have shown that when predators are killed off the herbivore population skyrockets and plants suffer -Wolf release into Yellowstone and other national parks led to increased diversity of wildflowers and waterfowl -Wildflowers and young trees increased due to reduction of herbivores like deer and elk -Waterfowl increased due to predation on smaller predators like fox and skunk which often kill these birds -Explain why there are more algae in lakes that have trout than lakes that have no fish -The graph shows that lakes with trout have a much smaller invertebrate population and more algae than lakes without fish. The reason is that trout eat the invertebrates, like snails, that consume algae. More trout = few invertebrates. Fewer invertebrates = more algae.

ecology basics

-describes the interrelationships between organisms and their environment -Ecologists are interested in relationships at many different levels, including: 1. Individual organisms, where they live and how they fit into their environment -- their adaptations 2. Populations: groups of individuals of the same species living together in the same place at the same time 3. Community: all the populations living together in the same place at the same time 4. Ecosystem: the community plus its non-living environment 5. Biome: a large region with distinct plants, animals, and microbes that have developed under specific soil and climatic conditions 6. Biosphere: all the ecosystems of the earth together; the total of all living things and their environments

Competitive exclusion principle

-each species must have its own niche. The more the niches of two species overlap, the more they compete -species must partition, or share, the environment or one of the species will go extinct -Character displacement allows a species to modify its resource use to minimize niche overlap in the presence of a competitor -Paramecium species demonstrate the problem with competition -P. aurelia and P. caudatum can each survive alone in the test tube, but together only one will survive, and it's always aurelia -In environmental partitioning each species specializes in one particular subdivision of the environment -P. aurelia and P. busaria can partition the environment by eating different prey

Kingdom Plantae, the plants:

-multicellular, photosynthetic organisms with rigid cell walls -land plants evolved from aquatic green algae by evolving adaptations that allowed them to survive on land -Land plants differ from water plants bc land plants need adaptations to help them find water and prevent its loss from the body -They prevent water loss by a waterproof covering called the cuticle -Cuticles prevent carbon dioxide diffusion, so they have openings called stomates -Stomates also allow water loss, so plants can open and close them with guard cells to respond to changing conditions -Most plants have evolved a system of tubes called a vascular system that allows them to transport materials around their bodies -Plant vascular tissue has two parts 1) xylem moves water and minerals around the body 2) phloem moves food (sugar from photosynthesis) -Air provides much less physical support than water -Plants evolved a strengthening compound called lignin -makes them strong enough to stand up in air -found mainly in xylem cells -Land plants' needs are met in two different environments: they need to grow in the air to get sunlight, but also in the soil to get water -phloem is needed to move food to parts of the plant that can't photosynthesize -Gametes cannot just be shed into the environment as algae do -Gametes and young, small plants need to be protected from drying -Cones, pollen and flowers are reproductive innovations evolved by higher groups of plants to assist in successful reproduction

mutualism competition

-mutualism: both species benefit -Typical benefits are food, defense, and help with dispersal -Trophic mutualism: refers to food or resource mutualism -example: cleaner fish, mycorrhizal fungi and plant roots -Defensive mutualism: one organism defends another in return for a reward -ants protect aphids and consume their honeydew -ex: Ants and ant plants -Dispersive mutualism: since plants can't move they often use animals to move their pollen and seeds or fruits for them -commensalism: one species benefits and the other is not affected -birds that follow grazing animals and eat the insects they disturb -Spanish moss that hangs from limbs but does not harm trees -amensalism: one species is harmed, the other is unaffected -Mammals trampling plants -competition: both species are harmed by using the same resource. -Example: plants competing for light -Exploitation competition: each organism tries to get as much of the competed resource as possible -spiders and lizards competing for insect prey -Interference competition: one species directly interferes with a competitor's ability to get resources, for example by blocking it or scaring them away -Lions guarding a kill from hyenas is an example , or two different kinds of birds or fish fighting over a food source Interference competition also occurs when kudzu vines grow over their host leaves and branches

Mass Extinctions

-short periods of time during which many species become extinct -There have been 5 mass extinctions in the past, and one is occurring now -There is evidence that an asteroid did impact on the Earth when the dinosaurs became extinct -The ancestors of mammals survived because they were small, rat-like, nocturnal creatures who could eat anything and tolerate almost any conditions -Evidence for asteroid impact: Asteroids have much more of the element iridium than the Earth has. -An asteroid impact would throw iridium-laced dust into the atmosphere, which would settle later and produce an iridium spike in rocks -Today, the majority of extinctions occur due to habitat destruction -- loss of the habitat that organisms need to live -Most environmental loss is due to conversion of wild habitats to human use as a direct result of increasing human populations -Other causes of human-induced extinction: -Overexploitation by humans (Especially in marine species currently), introduced invasive species that take over from native species (Examples: kudzu, lionfish, water hyacinth), climate change leads to extinction or relocation of populations

What types of symbiotic associations do you see in the following picture? Justify your choice, but there may be more than one. See if you can find a benefit to each species.

1. Crab with sponge growing on its shell -Mutual: the crab get camouflage, the sponge gets moved around and bits of food stirred up or dropped by the crab. 2. Squirrel eating nut vs. Squirrel burying nut -The squirrel is a predator on the nut when eating it, but when it is burying the nut we see that there is an aspect of mutuality in that the squirrel disperses and plants the nuts, and does not find them all during the winter. 3. Owl in hollow tree -Commensal: the owl does not harm or help the tree. It does not dig out the hole, just lives in holes that it finds. 4. Mites living in a person's eyelash follicle -Commensal, they are harmless to people

Do you think these species are more r-selected or more k-selected? 1. dogs 2. mosquitoes 3. pine trees 4. Minnows 5. dolphins

1. Dogs - more k selected 2. Mosquitoes - more r selected 3. pine trees - more k selected (but near the  middle) 4. Minnows - more r selected 5. Dolphins - more k selected

population growth types types of population growth KEY POINT: Populations are studied in terms of their spatial distributions, sizes, and life history, and growth characteristics.

1. Exponential growth (J-shaped curve): each generation grows at a constant rate from the previous generation -Each generation is multiplied by a number to get the size of the next generation -the number is based on biological differences between species -If r is 10% (0.1) and the population starts out at 100 -generation 2 is 100 + 100 (0.1) = 110 (10 are added) -generation 3 is 110 + 110 (0.1) = 121 (11 are added) -generation 4 is 121 + 121 (0.1) = 133 (12 are added) -Each generation adds more to the population than the generation before, and this continues as long as growth is exponential 2. Logistic growth (S-shaped curve): is limited by the carrying capacity of the environment -It starts out exponential, but as the population nears the carrying capacity, growth levels off and stops -The carrying capacity is the maximum population size that can be sustained indefinitely in an environment, meaning that it does not harm its environment -Population growth is controlled by density-dependent and density-independent factors -Density-independent factors control all populations in a similar manner, regardless of size -ex= extreme weather, human pollution, toxins, etc. -Density-dependent factors increase in severity as the population increases -more common, usually involved in controlling logistically growing populations ex= Include food and water availability, space to live, disease, waste production, etc. 3. Survivorship curves: species are characterized by different patterns of survivorship throughout their lives -Type I species mostly survive childhood and die later in life due to age, predation or illness -Large, complex animals -Type III produce many more offspring than can survive and provide little parental care -Individuals that get through the juvenile period are likely to live out their life span -Type II species have a steady rate of decline throughout the lifespan -Small prey animals and birds often fall into this category -Humans show type I survivorship now, but showed type III in the 17th century

If the birth rate is 1.5%, the death rate is 0.8%, the immigration rate is 2.3% and the emigration rate is 0.3%, what is the total growth rate?

1.5% + 2.3% - 0.8% - 0.3% = 2.7% growth rate

Think about adaptations needed for a primate to become bipedal. List as many as you can. Include arms and legs, pelvis, knees, feet, neck/head in your thinking.

Even though the skeletons are not that different, when you think about it there are a huge number of small changes that have to be made. The angle between the skull and backbone is different. The length of the arms and legs change. The orientation of the knees and leg bones is different. The pelvis has to hold the organs like a bowl. The feet flatten out. And remember - all of these changes have to be adaptive for the animal at the time, you can't get evolve them in hope that they'll be useful later on.

Draw a branching evolutionary tree showing the correct evolutionary relationships between an extinct primate ancestor, the Old World monkeys, humans, the New World monkeys, an extinct ape common ancestor, and chimpanzees. Be sure you label all of these on your evolutionary tree.

Extinct primate ancestor ->New World Monkeys and ->Old World Monkeys Old World Monkeys ->Extinct ape ancestor Extinct ape ancestor ->chimps ->humans

Match Homo erectus, gorilla, Homo neanderthalensis, Australopithicus afarensis with the correct skull. EXPLAIN WHY. Look at teeth, brow and cheek ridges, face shape, brain size

In order from most primitive to more advanced: 2. gorilla: look at the big teeth and the actual brain case is very small, although the bone ridges used for jaw muscle attachments make it look big it is not 4. Australopithicus afarensis: big brow and cheek ridges, small brain case 1. Homo erectus: Intermediate sized brow ridges and brain case 3. H. neanderthalensis. Nearly modern looking skull

Scientific classification of humans

Kingdom Animalia (animals) Phylum: Chordata (notochords) Subphylum Vertebrata (backbones) Class: Mammalia (hair, milk) Order: Primates Family: Hominidae Genus: Homo Species: sapiens

List the 2 major habitats that you see in the amazon rainforest ecosystem. Subdivide each into at least 3 more specialized habitats.

River: shore, shallow water, deep water, bottom (maybe more than one type depending on if there are mud, sand, and gravel bottoms in different places) Forest: soil, leaf litter, understory, tree trunks, canopy

Parasites, like other organisms, are highly adapted to their environments. Tapeworms are parasites that inhabit the mammalian gut. Describe how natural selection could go from a planarian-like ancestor with a primitive digestive system to a tapeworm with no digestive system.

Since tapeworms live in digested food there is no need to digest their own, so the tapeworms that spent less energy on digestion and more energy on reproduction were more successful, until finally modern tapeworms have no digestive system and essentially spend all of their energy on reproduction. The odds of any one egg finding its way to another digestive system are extremely small, so they make up for it by producing millions and millions of eggs.

conservation

a. Corridors = linkages between habitats b. Direct economic benefit = medicines from plants c. Pollution = toxic wastes d. Preserve species = zoos and parks e. Captive breeding = pros f. Extinction = loss of a species g. does not conserve habitat = cons h. biological preserves and parks = protected habitats i. habitat destruction = deforestation j. indirect economic benefit = water filtration by wetlands k. overexploitation = unregulated fishing l. ethical/aesthetic benefit = part of national heritage m. Exotic species introduction = cats and rats brought to islands

a. What trophic level is a shrew (mole)? What proportion of the sun's energy do shrews have access to? b. Describe the trophic level of the hawk and its access to energy

a. The shrew is a secondary consumer, with access to about 1% of the sun's energy (10% for the primary consumers and then 10% of that for the secondary consumers). b. The hawk is a tertiary consumer with access to 10% of the shrew's level or only 0,1% of the sun's energy.

These are really important evolutionary innovations in animals. Explain what the primitive condition was and why the advanced conditions were selective advantages for each of these a. complete digestive system b. coelom c. segmentation

a. primitive condition was incomplete digestive system, the selective advantage was more efficient use of food and ability to tailor different parts of the digestive system for different jobs b. the primitive condition was no coelom, the selective advantage was more space to grow bigger and separate organs from movement of the body c. the primitive condition was no segmentation, the selective advantage was ability to grow bigger by just repeating what you could already make without needed new genes or structures.

What type of distribution does the human population show, and why? Since more than one answer might be right, you have to explain your reasoning.

It depends on the scale at which you think about distribution. The best answer is clumped, since most people live in cities surrounded by countryside with a much lower population density. But if you think about distribution of people within a city, they might be more or less uniformly distributed in their houses and apartments. Or within a smaller area like a beach or a shopping mall people might be randomly distributed.

Explain why the fundamental niche is larger and based on abiotic factors and why the realized niche is smaller and based on biotic factors. Talk about a real plant or animal to help guide your thinking.

-There are a lot of ways to answer this question, but you need the following ideas. Abiotic conditions define the basic survivability of a habitat: can the species tolerate freezing or low rainfall, for example. That determines the fundamental niche which includes all of the places a species could possibly live and not be killed by the environment. -The realized niche must include the importance of competition, and organisms better adapted to conditions outcompeting those that could live there but are not as well adapted to those specific conditions.

4 major groups of plants

-based on their structures and type of reproduction -Bryophytes are the most primitive type of plants -Bryophytes are only partially cutinized and have no vascular tissue -They remain small so water can diffuse around the body, and they live in moist environments -Bryophytes don't have true leaves or roots, they have green photosynthetic leaf-like structures -Some have root-like rhizoids under the body but they only help attach the plant, they are not specialized for water absorption -Bryophytes produce sperm that swim from male to female plants, another reason that they must remain small -After fertilization mosses also form spores and release them into the air to disperse new plants -Seedless vascular plants evolved strong vascular tissue to transport food and water, allowing them to grow taller and bigger than mosses -They have true leaves and roots -The main evolutionary innovation of the seedless vascular plants was lignin, which allowed the evolution of xylem and phloem -Mature ferns produce spores in sori on the undersides of leaves -next evolutionary advance was the seed, first seen in the gymnosperms or cone-bearing trees, the pines, firs, redwoods, etc. -Gymnosperms include the tallest and oldest plants known -Gymnosperms' reproductive structures are very small and protected inside cones -Female or seed cones produce the ovules -Pollen is produced in separate pollen cones -Gymnosperm sperm doesn't swim; it is moved in the air by floating pollen -After pollen lands on the seed cone, it germinates and forms sperm -These fertilize the eggs, which develop into seeds containing an embryo and some nutrition -Most plants today are flowering plants or angiosperms; they have a unique reproductive organ, the flower -Angiosperm also form seeds, which are protected inside fruits -The greater speed of angiosperm reproduction allowed angiosperms to take over much of the area previously occupied by gymnosperms -Angiosperms gave up fighting the height war and some evolved into smaller plants

ecosystems

-have important abiotic and biotic components -Ecosystems are large areas which can be broken down into many habitats, specific areas in which organisms live -a coastline ecosystem contains lowlands, shallow water, deep water, beaches, dunes, etc. -A set of unique biotic and abiotic components define each habitat -Habitats provide organisms with physical and biological conditions they need to survive -Each habitat supports a unique community -If change or loss of a habitat occurs faster than evolutionary change can keep up, the result will be extinction of organisms adapted to that habitat

A biology student was studying mice in an abandoned farm field. Her first trapping yielded 200 mice, and in the second trapping 300 mice were caught of which 50 were already marked. What was her estimate of the mouse population? (Remember N = Mn/R)

N = 200x300/50 = 1200

Explain how character displacement could evolve, using the ideas of natural selection.

On Santa Cruz Island, G. fulginosa and G. fortis live together. Since fortis is bigger, it competes for larger seeds better and indirectly kills off larger fulginosa that tend to compete directly with it by starving them out. They do not reproduce to form offspring with large beaks. On Los Hermanos, without that competition, larger fulginosa can survive, reproduce, and produce offspring with larger beaks that are also successful.

Would r-selected or k-selected species do better growing along the sides of highways? Explain your answer.

Since the sides of highways are variable, poor quality environments that would be easy for stray seeds to get into, r-selected species would do better there.

populations vs race KEY POINT: People do differ from one another, but their differences come from their population of origin, not their "race".

-A population is a group of organisms of the same species which interbreed with one another under natural conditions -A species is a group of organisms which can interbreed, but each species is subdivided into a number of smaller populations -The giant swallowtail butterfly ranges over the eastern US, but a butterfly in Iowa is unlikely to mate with one in North Carolina -They belong to different populations -Humans form many different populations, distinguishable by ethnic, religious, language, and cultural differences -While populations at great distances from one another may differ greatly, neighboring populations are more similar due to gene exchange -There is a gradual change from European to Asian or African to European -South African->North African->South European->Northern European -Although people form many different populations, the notion of race is biologically MEANINGLESS in humans -There is no evidence for genetic similarity among populations that share superficial characteristics like skin or hair color -Biologically, a race is a population which differs genetically from other populations of the species -Biological races may be groups in which speciation is underway but not completed, like the apple maggot fly -Genetic differences can be expressed in two ways: 1) a race may have alleles that other races do not have AND 2) a race may have different allele frequencies than other races -either or both of these conditions indicate that a population has evolved in isolation from other populations for a substantial period of time -Neither of these conditions is met in humans -The sickle cell trait is often linked with Africans or a Black race -Actually the allele is associated with geography, not race only central and western Africa populations have a high incidence of this allele -some White and Asian populations also carry the allele -Allele frequencies do not differ among racial groups -Allele frequencies differ among populations, but a group of populations classified as "Black" are not necessarily more similar to one another than they are to a group of populations classified as "White" -What about obvious differences in skin color, hair texture, eye shape? -Similarity in skin color among people in nearby parts of the world is likely due to convergent evolution, not relationship -In convergent evolution similarity is due to the same environment selecting for the same outcome, rather than genetic relationship being responsible for the similar outcome -Humans migrating north out of Africa acquired mutations changing their dark skin color to a lighter shade as they adapted to the lower UV rays in the sunlight -Groups ending up in similar conditions would look similar but not necessarily be closely related -Their strongest genetic affinities would be to their African population of origin -The concept of race that we are familiar with in the US today is a social definition only, with no scientific basis -It was originated by Europeans, to distinguish themselves from people around the world and justify the way they (Europeans) treated native peoples

hominids

-include all extinct and living orangutans, gorillas, chimps, bonobos and humans -Characteristics of hominids: no tail (but retain vestigial tailbone) -more erect posture, increased thumb flexibility, and larger brain than monkeys

Stop and Think

1. Leaves: -Major function: Photosynthesis -Can be modified for: capturing insects -Helps capture light: cell shapes -Used in gas exchange: stomates -Absorb: sunlight 2. Stems: -Modified stem: potato -Transports sugars: phloem -Transports water: xylem 3. Roots: -Increase surface area: root hair -Sense organ: root cap -Major function: water/mineral uptake -Modified for oxygen uptake: knees

a. Think of 3 specific differences between living in water and living on land.  b. What evolutionary innovations could or did animals come up with to deal with these differences as they adapted to living on land?

a. water is always available so drying out is not a problem, water provides support for the body, water provides much more stable temperatures, water provides protection from UV light. And more. We will cover the innovations in the coming slides.

population KEY POINT: Aspects of life history are selectable adaptations to different environments.

1) POPULATION CHARACTERISTICS: -a population is a group of organisms of the same species that interact and mate with one another -for humans, the entire world is now a single population 2) POPULATION DISPERSION (distribution in space): A. Clumped: individuals gather around a specific resource, type of environment or mating area -Cottonwoods and willows need a lot of water and are found near streams and rivers -Schools of fish group for protection -most common distribution pattern B. Uniform: each organism needs to control a similar size territory or resources are sparse -Birds need to control a large enough territory to supply food for themselves and their families -spiders distribute themselves uniformly in grass or bushes because they don't like to be too near one another C. Random: organisms don't care or can't control how near they are to their neighbors -rare among mobile animals -do not interact with others much and resources are fairly abundant -ex: dandelions, trees in a forest, sponges 3) POPULATION SIZE: -Most important characteristic ecologically -Can be determined in various ways- A. direct counting: human censuses, small areas B. Mark and recapture: a group of animals is captured, marked, and released, and then later a second group is captured -In the second group, some will be recaptures of animals marked the first time -The percentage of marked individuals in the second group is assumed to represent their percentage in the entire population, so using a ratio we can determine the approximate size of the population: N/M = n/R N= the whole population M = the number of marked individuals (caught in the first trapping) n = the number of animals caught in the second trapping R = the number of marked individuals among those caught in the second trapping -Since we want to find N, we rearrange the equation to say N = Mn/R -If the first trapping yielded 53 beetles, and in the second trapping 78 beetles were caught of which 14 were already marked, we would estimate the population size as (53)(78)/14 = 295 C. Sampling: count the individuals in a random sample of the area and assume that they are found in the same proportion in other parts of the area -This works best with plants or other organisms that don't move around much -to sample larger organisms, a line transect may be used -A rope is stretched through an area and any plants within a meter of either side are counted -REPRODUCTIVE STRATEGIES, like other characteristics, can be naturally selected- 1. Semelparity is one large reproductive effort in the life of the organism: it reproduces and then dies (salmon spawning) -Found in organisms adapted to favorable, predictable conditions -Examples: salmon, grasshoppers, octopuses, Agave 2. Iteroparous species: produce fewer offspring at a time but have many reproductive episodes -Seen in organisms adapted to poorer or more variable conditions -Ex= perennial plants, most large mammals, sharks, most birds 3. Masting is the synchronized production of highly variable numbers of offspring: huge numbers in some years, smaller in others -a variant of iteroparity designed to reduce predation -Age at first reproduction - In a growing population, a few offspring early can increase an individual's fitness more than many offspring later. -But organisms often have more resources available to them as they age -Tradeoff: reproduce early with a few offspring or reproduce later with more offspring 4. Switching sex - Some plants and animals can convert from male to female -Other species can convert from female to male - Occurs in fish when the only male in a group dies; one of the females will become male 5. Life History strategies: r-selected vs. k-selected -naturally selected adaptations -Examples include life span, age at first reproduction, growth rate -r-selected species are opportunistic: short maturation time, breed at a young age, short lifespan, small offspring not well cared for, high mortality rates -adapted to variable or low-quality environments; good colonizers; weedy -Examples include dandelions, insects, bacteria, mice -k-selected species have long maturation time, breed later in life, have a longer lifespan with larger offspring that are cared for and have a lower mortality rate -Adapted to more predictable environments. -Examples: elephants, apes, humans, oaks