Chapters #34, 35, 36, and 37: Ecology

Streams and Rivers

-Moving fresh water that travels from a source to a mouth.

Savanna

-Hot, dry, and prone to fires. -Scattered bushes. -Ex: New Mexico

Estuaries

-Where saltwater meets freshwater.

Desert

-Hot, dry, and has little vegetation. -Found between the Tropic of Cancer (23.5 Degrees N) and 30 Degrees North, and the Tropic of Capricorn (23.5 Degrees S) and 30 Degrees South. -Ex: Egypt

Photic Zone

-The photic zone is the area of the ocean with the most light. It is the uppermost layer of water.

Aphotic Zone

-The aphotic zone is the portion of a lake or ocean where there is little to no sunlight. The only light source is bioluminescence.

Community

-A biological community is an assemblage of populations of various species living close enough for potential interaction. -Ex: Animals and plants surrounding a watering hole in southern Africa are members of a savanna community. -Ex: Humans, mice, bacteria, and spiders are all part of the MHS community. -A community's interactions include competition, predation, herbivory, symbiosis, and disease.

Tundra

-A biome that is extremely cold, dry, and home to permafrost. -Experience short summer seasons in which the soil becomes swampy and marshy. -An alpine tundra occurs on mountains at altitudes above the treeline. -An arctic tundra is found at the poles. -Ex: Alaska

Lakes

-A body of water that is surrounded by land that can be freshwater or saltwater.

Coniferous Forest

-A forest populated by cone-bearing evergreen trees. -Ex: Pacific NW

Population

-A population is a group of individuals of a single species living in the same general area at the same time. -Interactions within a population include mating and reproducing. -Dynamic biological processes influence population density. -One can enter a population through birth or immigration, and one can leave by death or emigration. -Populations are regulated by a complex interaction of biotic and abiotic influences. -There are two general questions about regulation of population growth: What environmental factors stop a population from growing? Why do some populations show radical fluctuations in size over time, while others remain stable?

Reproductive Rates

-A reproductive table, or fertility schedule, is an age-specific summary of the reproductive rates in a population. -It describes reproductive patterns of a population. -In animals, parental care of smaller broods may facilitate survival of offspring. -Organisms with parental care undergo k-selection. Organisms without parental care undergo r-selection.

Animal Signals and Communication

-A signal is a behavior that causes a change in another animal's behavior. The transmission and interaction of signals is called communication. -Signals can be chemical, like pheromones, visual, auditory, or tactile. -Ex: Chemical signals were released in a tank containing fish. The fish all huddled in a corner as there are safety in numbers.

Survivorship Curves

-A survivorship curve is a graphic way of representing the data in a life table. -The survivorship curve for Belding's ground squirrels shows a relatively constant death rate. -Survivorship curves can be classified into three general types: Type I, Type II, and Type III. -Type I curves represent large animals like humans and elephants who live to be old at which point the death rate increases. -Type II curves represent an equal/constant amount of deaths and births per year. An example would be squirrels and other rodents. -Type III curves represent animals like clams and insects in which many die at an early age.

Aquatic Biomes

-Abiotic and biotic factors influence the structure and dynamics of aquatic biomes. -Varying combinations of biotic and abiotic factors determine the nature of biomes. -Biomes are the major ecological associations that occupy broad geographic regions of land or water. -Aquatic biomes account for the largest part of the biosphere in terms of area. -They can contain fresh or saltwater. -Oceans cover about 75% of Earth's surface and have an enormous impact on the biosphere. Their high specific heat helps to regulate temperature. -Many aquatic biomes are stratified into zones or layers defined by light, penetration, temperature, and depth. -Exs: Lakes, Wetlands, Streams, Rivers, Estuaries, Intertidal Zones, Oceanic Pelagic Biome, Coral Reefs, and the Marine Benthic Zone

Abiotic Factors

-Abiotic factors are the not alive components of an ecosystem. -Ex: Temperature, Water, Sunlight, Wind, Rocks and Soil, pH, and Mineral Composition

Tropical Forest

-Greatest diversity of species in all of the biomes. -Quick evapotranspiration cycle. -Hot, wet, and near the equator. -Found between the Tropic of Cancer (23.5 Degrees N) and the Tropic of Capricorn (23.5 Degrees S). -Ex: Hawaii

Factors of Climate

-Air moves from high to low pressure causing winds. Winds are named by where they're coming from. -Oceans and their currents and large lakes moderate the climate of nearby terrestrial environments. Water has a high specific heat helping it to regulate temperature. Convection currents above the water move air with water vapor in it leading to rain. -Wind can be stopped by mountains which therefore stops the movement of rain clouds. This causes a rain shadow, or desert, on one side of the mountain. -Ex: Mojave Desert, Sierra Nevada Mountain -The tallest mountain is Chimborazo. -The angle of the sun leads to many seasonal changes in local environments. -Lakes are sensitive to seasonal temperature change and experience seasonal turnover. -The densest water, which is about 4 degrees celsius, sinks creating currents that bring nutrients. -Turnover occurs in the autumn and springtime. The turnover is caused by the different densities of water.

Wetlands

-An ecosystem that is flooded by water either temporarily or seasonally. -O2 free processes occur here.

Biotic Factors

-Biotic factors are the living components. -Biotic factors that affect the distribution of organisms may include interactions with other species, predation, and competition. -Ex: On a graph depicting the relationship between sea urchins and limpets, it is seen that the urchins are the major seaweed eaters. The graph also shows that by affecting/removing one organism in an ecosystem, you affect all of them.

The Carbon Cycle

-Carbon-based organic molecules are essential to all organisms. -Photosynthetic organisms convert CO2 to organic molecules that are used by heterotrophs. -Carbon reservoirs include fossil fuels, soils and sediments, solutes in oceans, plant and animal biomass, the atmosphere, and sedimentary rocks. -CO2 is taken up and released through photosynthesis and respiration; additionally, volcanoes and the burning of fossil fuels contribute CO2 to the atmosphere. -The largest reserve of CO2 is the atmosphere.

Climate and Terrestrial Biomes

-Climate has great impact on the distribution of organisms as seen on a climograph. -The climograph shows the temperature and amount of precipitation in each biome. -Terrestrial biomes are often named for major physical or climate factors and for vegetation. -Stratification is a key feature of terrestrial biomes. -Terrestrial biomes usually grade into each other, without sharp boundaries. -The area of intergradation, called an ecotone, may be wide or narrow.

Coevolution

-Coevolution is reciprocal evolutionary adaptations of two interacting species. -The term is often used too loosely in describing adaptations within a community. -There is little evidence for true coevolution in most interspecific interactions.

Defense Adaptations

-Cryptic coloration, or camouflage, makes prey difficult to spot. -Animals with effective chemical defense, like poison, often exhibit bright warning coloration, called aposematic coloration. Predators are particularly cautious in dealing with prey that display such coloration. -In Batesian mimicry, a palatable or harmless species mimics an unpalatable or harmful model. -Ex: Hawkmoth Larva & Green Parrot Snake -In Müllerian mimicry, two or more unpalatable species resemble each other. -Ex: Cuckoo Bee & Yellow Jacket Wasp

Decomposition and Nutrient Recycling

-Decomposers (detritivores) play a key role in the general pattern of chemical cycling. -Rates at which nutrients cycle in different ecosystems vary greatly, mostly as a result of differing rates of decomposition. -The rate of decomposition is controlled by temperature, moisture, and nutrient availability. -The tropical rainforest has a low amount of nutrients as thousands of plants grow there and use up the soil's nutrients, but there is fast decomposition. -The tundra has a soil full of nutrients as the ground is frozen and nothing can grow there. However decomposition in cold and wet ecosystems is very slow. -Decomposition in anaerobic muds, such as a bog, is also slow. -The Hubbard Brook Experiment revealed that deforested areas had high rates of water and nutrient loss.

Demography

-Demography is the study of the vital statistics of a population and how they change over time. -Death rates and birth rates are of particular interest to demographers.

Detritivores

-Detritivores, or decomposers, are consumers that derive their energy from detritus, nonliving organic matter. -Prokaryotes and fungi are important detritivores. -Decomposition connects all trophic levels as all organisms eventually die. -Wherever fungi are, something dead is nearby. -Ex: Mushrooms growing on a dead tree trunk.

Dispersal and Distribution

-Dispersal is movement of individuals away from centers of high population density or from their area of origin. -Dispersal contributes to global distribution of organisms. -Natural range expansions show the influence of dispersal on distribution. -As the amount of species increases, they must disperse due to a finite amount of resources. -Ex: Humans had to migrate out of Africa to follow their food. -Species transplants include organisms that are intentionally or accidentally relocated from their original distribution. -Species transplants can disrupt the communities or ecosystems to which they have been introduced. -Ex: The transport of lumber can bring invasive species to new places.

Disturbance

-Disturbance influences species diversity and composition. -Decades ago, most ecologists favored the view that communities are in a state of equilibrium. -Recent evidence of change has led to a nonequilibrium model, which describes communities as constantly changing after being buffeted by disturbances. -A disturbance is an event that changes a community, removes organisms from it, and alters resource availability. -Fire is a significant disturbance in most terrestrial ecosystems like the chaparral and savanna biomes. -It is often a necessity in some communities. -Ex: Fire cycles nutrients into the soil from the materials that it burns. The soil is fertilized and plants can grow back. -The intermediate disturbance hypothesis suggests that moderate levels of disturbance can foster higher diversity than low levels of disturbance. -The large-scale fire in Yellowstone National Park in 1988 demonstrated that communities can often respond very rapidly to a massive disturbance.

Temperate Grassland

-Has deep, nutrient-rich soil that supports agriculture. -Ex: Midwest

Chaparral

-Has vegetation consisting chiefly of tangled shrubs and thorny bushes, known for winemaking, near the mediterranean, and prone to fires. -Ex: California

Herbivory

-Herbivory refers to an interaction in which an herbivore eats parts of a plant or algae. -It has led to evolution of plant mechanical and chemical defenses and adaptations by herbivores. -Ex: Spines, Thorns, Taste, Poison

Keystone Species

-Dominant and keystone species exert strong controls on community structure. -In general, a few species in a community exert strong control on that community's structure. -Two fundamental features of community structure are species diversity and feeding relationships. -In contrast to dominant species, keystone species are not necessarily abundant in a community. -They exert strong control on a community by their ecological roles, or niches though they may not be the most abundant. -Ex: Without sea stars mussels would take over intertidal communities leaving no room for seaweed to grow or for any other organism. -Ex: Killer whales keep the amount of sea otters in check which in turn keep the number of urchins in check which feed on seaweed and keep its amount at a good level.

Dominant Species

-Dominant species are those that are most abundant or have the highest biomass. -They exert powerful control over the occurrence and distribution of other species. -One hypothesis suggests that dominant species are most competitive in exploiting resources. -Another hypothesis is that they are the most successful at avoiding predators.

Limits on Food Chain Length

-Each food chain in a food web is usually only a few links long. -Two hypotheses attempt to explain food chain length: the energetic hypotheses and the dynamic stability hypotheses. -The energetic hypothesis suggests that length is limited by inefficient energy transfer. -The dynamic stability hypothesis proposes that long food chains are less stable than short ones. -Most data supports the energetic hypothesis. -Trophic efficiency is the percentage of production transferred from one trophic level to the next. -Trophic efficiency is multiplied over the length of a food chain. -Approximately 0.1% of chemical energy fixed by photosynthesis reaches a tertiary consumer. -A pyramid of net production represents the loss of energy with each transfer in a food chain. -In a biomass pyramid, each tier represents the dry mass of all organisms in one trophic level. -Most biomass pyramids show a sharp decrease at successively higher trophic levels.

Earth's Movement

-Earth is an oblate spheroid meaning it is fatter around the middle. -At the poles light hits Earth at an angle, but at the equator light hits Earth directly resulting in 12 hour days and 12 hour nights. -Sunlight takes 8 minutes to reach Earth. -The combination of Earth's 23.5 degree tilt and Earth's revolution around the sun causes the seasons. -When the Earth is tilted towards the sun, summer is experienced. When the Earth is tilted away from the sun, winter is experienced. -A solstice occurs when the sun reaches its highest or lowest point in the sky at noon, marked by the longest and shortest days. -An equinox occurs when day and night are of equal length. -The Earth revolves (cause of the seasons) and rotates (cause of day and night) at the same time.

Ecological Succession

-Ecological succession is the sequence of community and ecosystem changes after a disturbance. -Primary succession occurs where no soil exists when succession begins. -Ex: Retreating Glaciers, Volcanic Island -The rock breaks and plants grow and die creating topsoil for more plants and trees to grow in. -Secondary succession begins in an area where soil remains after a disturbance. -Ex: Fire

Interspecific Interactions

-Ecologists call relationships between species in a community interspecific interactions and relationships between the same species intraspecific. -Interspecific interactions affect species survival and reproduction. -Competition (-/-): The interaction can be detrimental to both species. -Predation (+/-): The predator is positively affected and the prey negatively. -Herbivory (+/-): The organism eating is positively affected and the plant negatively. -Parasitism (+/-): A parasite feeds off a host. Ex: Tapeworm, Tick -Disease (+/-): The host is negatively affected by a virus who lives off the host and reproduces. -Mutualism (+/+): The interaction is beneficial to both species. Ex: E. coli in your digestive system break down food for you and are provided with shelter and nourishment. -Commensalism (+/0): One species benefits from the interaction, and the other species in unaffected by it. Ex: Lichen on the back of a turtle's shell.

Ecology

-Ecology is the scientific study of the interactions between organisms and the environment. -These interactions determine distribution of organisms and their abundance. -Ecology reveals the richness of the biosphere. -Ecology provides the scientific understanding underlying environmental issues. -Rachel Carson is credited with starting the modern environmental movement.

Disease

-Effects of disease on populations and communities are similar to those of parasites. -Pathogens, disease-causing agents, are typically bacteria, viruses, or protists. -They try to illicit symptoms to spread the virus instead of flying under the radar. -Ex: Throw Up, Coughing, Sneezing

Patterns of Dispersion

-Environmental and social factors influence the spacing of individuals in a population. -In a clumped dispersion, individuals aggregate in patches. A clumped dispersion may be influenced by resource availability and behavior. -Ex: For many animals such as wolves, fish, and whales, living in groups increases the effectiveness of hunting, spreads the work of protecting and caring for young, and helps exclude other individuals from their territory. Packs, pods, and schools, however, still need to interbreed to maintain genetic diversity. -A uniform dispersion is one in which individuals are evenly distributed. -It may be influenced by social interactions such as territoriality. -Ex: Penguins exhibit uniform spacing, maintained by aggressive interactions between neighbors. -In a random dispersion, the position of each individual is independent of other individuals. -Ex: Dandelions grow from windblown seeds that land at random and later germinate.

Temperate Broadleaf Forest

-Found in regions with hot summers, cold winters, and relatively frequent rain. -Ex: East Coast

Climate

-Four major abiotic factors of climate include temperature, water, sunlight, and wind. -Climate is the prevailing weather in an area. -Global climate patterns are determined largely by solar energy and the planet's movement in space. -Macroclimate consists of patterns on the global regional and local levels. -Microclimate consists of very fine patterns, such as those encountered by the community of organisms underneath a fallen log. -Microclimate is determined by finescale differences in abiotic factors. For example the environment under a log could be cool and damp, while outside could be hot and dry. -While climate is long term, weather is short term.

Energy Costs and Benefits

-Goal is to produce the most amount of work with the least amount of energy.

Global Carrying Capacity

-Human population growth has slowed after centuries or exponential increase. -No population can grow indefinitely, and humans are no exception. -The human population increased relatively slowly until about 1650 and then began to grow exponentially. -Earth can support about 10 billion people. We are at 7.5 billion people right now. -We are still experiencing exponential/j-curve growth.

Human Disturbance

-Humans are the most widespread agents of disturbance. -Human disturbance to communities usually reduces species diversity. -Humans also prevent some naturally occurring disturbances, which can be important to community structure.

Imprinting

-Imprinting incorporates both innate and learned behaviors and is generally irreversible. -Learning occurs at a specific time called the sensitive period. -In chicks for example, the tendency to respond is innate, but the outside world provides the imprinting stimulus; usually through the chick's mother. -Ex: One scientist had a flock of geese imprint on him. He had to lead them through migration up in a plane because they had to see him to follow him.

Commensalism

-In commensalism, one species benefits and the other is apparently unaffected. -Commensal interactions are hard to document in nature because any close association of two species likely affects both. -Ex: Egrets stand on the backs of water buffalo as they walk which kicks up grass and insects making food easier to find for the egrets.

Competition for Resources

-In crowded populations, increasing population density intensifies intraspecific competition for resources. This includes territory, health, and increased predation. -Health can be affected by increased population size as more organisms causes disease and toxic waste to spread faster.

Parasitism

-In parasitism, one organism, the parasite, derives nourishment from another organism, its host, which is harmed in the process. -Parasitism exerts substantial influence on populations and the structure of communities. -Parasite doesn't want you to know they are there. -Ex: Lice, Tick, Mosquito, Tapeworm, Leech -There are parasitic plants that latch on to trees taking their water and nutrients.

Innate Behaviors

-Innate behaviors are developmentally fixed due to strong genetic influences. All individuals exhibit the behavior despite environmental differences. They are influenced by environmental stimuli. -Innate behaviors are also known as fixed action patterns, or FAPs. -FAPs are a sequence of unlearned behaviors that are unchangeable and carried to completion upon initiation. They are triggered by an external stimulus, or "sign stimulus". -Ex: Stickleback fish attack other stickleback fish when they see their red belly's approaching the area that their mate has laid their eggs. Even when scientists put random shapes and objects with red undersides, the fish attacked. however when sticklebacks with no red belly came by, the fish let them pass. -Kinesis is a simple change in activity or turning rate in response to a stimulus. -Ex: Rolly pollys/pill bugs move around until they find a dark spot. -Taxis is a more or less automatic oriented movement toward (+) or away (-) from a stimulus. -Ex: Plants move toward (+) a light source. This is called positive phototaxis. -Ex: Fish swim against the flow of water to stay upright and have an easier time getting food.

Interactions b/w Organisms and the Environment

-Interactions between organisms and the environment limit the distribution of species. -Ecologists have long recognized global and regional patterns of distribution of organisms within the biosphere. -Many naturalists began to identify broad patterns of distribution by naming biogeographic realms. -Biogeography is a good starting point for understanding what limits geographic distribution of species. -Exs: Nearctic, Neotropical, Ethiopian, Palearctic, Oriental, and Australian

Competition

-Interspecific competition occurs when species compete for a resource in short supply. -Strong competition can lead to competitive exclusion, local elimination of a competing species. -The competitive exclusion principle states that two species competing for the same limiting resources cannot coexist in the same place. -In other words two species can't live in the same niche at the same time.

Learned Behaviors

-Learned behaviors are modified through specific experiences. They are influenced by environmental stimuli. -Habituation is the loss of response to stimuli that convey little or no information. -The "cry-wolf" effect is common when organisms eventually stop responding to alarm calls from members of their own species; if they are not followed by actual attacks. -Associative learning is the ability of an organism to associate one feature of the environment (stimulus) with another feature. -Operant conditioning is trial and error associated with an award or punishment. -Ex: A wolf plays with a porcupine and gets hurt. It learns to stay away. -Classical conditioning is a conditioned stimulus and award or punishment. -Ex: When the school bell rings, students know to leave. -Ex: Pavlov's Dog Experiment -Sometimes there are genetic and environmental influences. For example although there is a strong genetic component, learning plays a major development in the song's of birds. -Spatial learning is the modification of behavior based on experience with landmarks in the environment.

Biogeochemical Cycles

-Life depends on recycling chemical elements. -Gaseous carbon, oxygen, sulfur, and nitrogen occur in the atmosphere and cycle globally. -Less mobile elements include phosphorus, potassium, and calcium. -These elements cycle locally in terrestrial systems but more broadly when dissolved in aquatic systems. -A model of nutrient cycling includes main reservoirs of elements and processes that transfer elements between reservoirs. -All elements cycle between organic and inorganic reservoirs. -Cycles recycle nutrients. For example lake turnover recycles nutrients in the lake.

Life History Diversity

-Life histories are very diverse. -Species that exhibit semelparity or "big-bang" reproduction, reproduce once and die. -Ex: Fish and Insects -Species that exhibit iteroparity, or repeated reproduction, produce offspring repeatedly. -Ex: Humans -Life history traits favored by natural selection may vary with population density and environmental conditions. -K-selection, or density-dependent selection, selects for life history traits that are sensitive to population density. -Ex: Humans -R-selection, or density-independent selection, selects for the life history traits that maximize reproduction. -Ex: Insects

Oceanic Pelagic Biome

-Most of the ocean's waters far from shore, constantly mixed by ocean currents. -Most big animals live here.

Mutualism

-Mutualistic symbiosis, or mutualism, is an interspecific interaction that benefits both species. -Ex: The acacia tree has sugar deposits on its leaves that a species of ants like to eat. They act as guard ants killing all the herbivores that try to eat the trees leaves.

The Nitrogen Cycle

-Nitrogen is a component of amino acids, proteins, and nucleic acids. -The main reservoir of nitrogen is the atmosphere. Here it is inert. However this nitrogen can be converted to NH4+ or NO3- for uptake by plants, via nitrogen fixation by bacteria. -Organic nitrogen, N2, is decomposed to NH4+ by ammonification. NH4+ is decomposed to NO3- by nitrification. NO3- is converted to N2 by denitrification. -N2 is fixed from the atmosphere into plants to be consumed by humans for use in nucleotides and proteins. -Humans return nitrogen through their pee which contains ammonia. -Ammonia is also used in fertilizers to replenish N2 in the soil. This excess nitrogen can be brought to the ocean through run off causing excess seaweed growth which throws off the entire ecosystem.

The Phosphorus Cycle

-Phosphorus is a major constituent of nucleic acids, phospholipids, and ATP. -Phosphate (PO4^3-) is the most important inorganic form of phosphorus. -The largest reservoirs are sedimentary rocks of marine origin, the oceans, and organisms. -Phosphate binds with soil particles, and movement is often localized. -Water weathers rocks so that run off sweeps up its particles, dissolving phosphorus which is taken into plants. -Some will form sedimentation at the bottom of lakes which are returned to the surface to be weathered again as plate tectonics move.

Predation

-Predation refers to interaction where one species, the predator, kills and eats the other, the prey. -Some feeding adaptations of predators are claws teeth, fangs, stingers, and poison. -Prey display various defensive adaptations. -Behavioral defenses include hiding, fleeing, self-defense, and alarm calls. -Animals also have morphological and physiological defense adaptations. -Ex: Camouflage, Aposematic Coloration, and Mimicry.

Behavior Questions

-Proximate questions identify the immediate stimulus and mechanism of behavior. These are the "how" questions. -Ultimate questions address the evolutionary significance of how behavior contributes to survival and reproduction. These are the "why" questions. -Some behavior is innate and some is learned. -Ex: All humans are born with the startle response. The proximate question would be "How does this occur?". The answer would be the noise serves as a stimulus. The ultimate question would be "Why does this occur?". The answer would be to have better awareness of one's surroundings.

Mating

-Sexual selection is the process of seeking or attracting mates, choosing mates, and competing for mates. -Mating systems are classified as monogamous, when there is one male and one female, and polygamous, when there is one male and many females (polygyny), or one female and many males (polyandry). -Sexual selection results in intrasexual selection, which is same sex competition for mates, and intersexual selection, which is mate choice based on specific characteristics. -Competition for mates often involves agonistic behavior. The female most often chooses the mate.

Behavior and Habitat Selection

-Some organisms do not occupy all of their potential range. -Species distribution may be limited by habitat selection behavior. -Ex: Areas with more wood are more likely to be chosen as habitats for termites.

Foundation Species

-Some organisms exert influence by causing physical changes in the environment that affect community structure. -For example, beaver dams can transform landscapes on a very large scale. -Some foundation species act as facilitators that have positive effects on survival and reproduction of some other species in the community. -Ex: The presence of jancus in sea marsh allows for an increase in plant diversity.

Species Diversity

-Species diversity of a community is the variety of organisms that make up the community. -It has two components: species richness and relative abundance. -Species richness is the total number of different species in the community. -Relative abundance is the proportion each species represents of the total individuals in the community. -Two communities can have the same species richness but a different relative abundance. -A community with an even species abundance is more diverse than one in which one or two species are abundant and the remainder are rare. -Community 1 is more diverse. In Community 2 Tree A is the most abundant.

Intertidal Zones

-The area between the tide marks. -This area is exposed to air and underneath water.

Biosphere

-The biosphere is the global ecosystem; the sum of all the planet's ecosystems including both living and nonliving factors.

Age Structure

-The demographic transition is associated with various factors in developed and developing countries. -One important demographic factor in present and future growth trends is a country's age structure. -Age structure is the relative number of individuals at each age. -It is commonly represented in pyramids. -Ex: Afghanistan has a rapid growth with many more kids and than adults. The United States has a slow growth with relatively equal amounts of kids and adults. Italy has a decreasing population with less kids than adults. -Age structure diagrams can predict a population's growth trends. -They can illuminate social conditions and help us plan for the future.

Exponential Growth

-The exponential model describes population growth in an idealized, unlimited environment. -It is useful to study population growth in an idealized situation. Idealized situations help us understand the capacity at which species increase and the conditions that may facilitate this growth. -The exponential model can show rebounding populations. -Depicted by a "j-curve".

Coral Reefs

-The habitat for several species of fish making it the most diverse aquatic biome. -CO2 ruins it through ocean acidification.

Logistic Growth

-The logistic growth model includes the concept of carrying capacity. -Exponential growth cannot be sustained for long in any population. -A more realistic population model limits growth by incorporating carrying capacity. -Carrying capacity (K) is the maximum population size the environment can support. -Represented by an "s-curve" that levels off at carrying capacity. -Some populations overshoot K before settling down to a relatively stable density.

Marine Benthic Zone

-The lowest level of a body of water which includes the sediment surface, and some subsurface layers, i.e. the bottom of the ocean. -Crabs and lobsters live here.

Population Dynamics

-The study of population dynamics focuses on the complex interactions between biotic and abiotic factors that cause variations in population size. -Many populations undergo boom-and-bust cycles. -Boom-and-bust cycles are influenced by complex interactions between biotic and abiotic factors. -The line that experiences the boom/bust before the other is the prey. The lower line is the predator. -This is because on the biomass pyramid the prey are lower than the predators, therefore there are more prey.

Ecological Niches

-The total of a species' use of biotic and abiotic resources is called the species' ecological niche. -Ecologically similar species can coexist in a community if there are one or more significant differences in their niches. -As a result of competition, a species' fundamental niche may differ from its realized niche. -Resource partitioning is differentiation of ecological niches, enabling similar species to coexist in a community and avoid the competitive exclusion factor.

The Water Cycle

-The water cycle is driven by the sun. -Water is essential to all organisms. -Liquid water is the primary physical phase in which water is used. -The oceans contain 97% of the biosphere's water; 2% is in glaciers and polar ice caps, and 1% is in lakes, rivers, and groundwater. -Water moves by the processes of evaporation, transpiration, condensation, precipitation, and movement through surface and groundwater.

Equatorial-Polar Gradients

-There are more species at the equator than at the poles.

Trophic Structure

-Trophic structure is the feeding relationships between organisms in a community. -It is the key factor in community dynamics. -Food chains link trophic levels from producers to top carnivores. -A food web is a branching food chain with complex trophic interactions. A food chain is a part of a food web. -Food webs can be simplified by isolating a portion of a community that interacts very little with the rest of the community. -An organism can be on different levels in different chains. -Producers are always at the bottom obtaining there energy from the sun. Primary consumers, secondary consumers, tertiary consumers, and quaternary consumers follow.