EXAM 2 - BIO 301E

Allopatric speciation

"Other Country": A population forms a new species while geographically isolated from its parent population. A pop. gets divided into geographically isolated subpopulations. Gene flow is interrupted or reduced. (Ex. mountain ranges, glaciers, land bridges, or splintering of lakes)

Sympatric speciation

"Same Country": takes place in geographically overlapping populations. The reproductive barriers must come about without geographic separation. Smaller subset of conditions lead to this, so it's not as common. Some factors that can reduce gene flow within one population: Polyploidy, Habitat differentiation, Sexual selection, and Pollinator preference

Inferences from Darwin's observations

#1: Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals #2: This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations

Darwin's observations

#1: Members of a population often vary in their inherited traits (phenotypes) #2: All species can produce more offspring than the environment can support, and many of these offspring fail to survive and reproduce

Conditions / Assumptions for Hardy-Weinberg equilibrium

(a) there is no mutation, (b) no gene flow into/out of a population or between populations, (c) population must be very large, (d) all mating is random, and (e) there is no natural selection

Limitations of the Biological Species Concept

- Cannot be applied to fossils or asexual organisms (including all prokaryotes) -Emphasizes absence of gene flow, but gene flow can occur between "distinct" species (especially in plants).

Evidence for evolution

- Fossils - Comparative anatomy (the study of how body structures differ among species) - Embryology (the study of developing organisms in the period from fertilization to birth) - Biochemistry - Genetics

Derived adaptation of tetrapods

- Four limbs, and feet with digits - A neck, which allows separate movement of the head - Fusion of the pelvic girdle to the backbone - The absence of gills (except some aquatic species) - Ears for detecting airborne sounds

Homo naledi

- Placed in genus Homo due to similarities with our lineage. - Small brain - Shoulder, upper limb and hand adapted to climbing. - Lower limb and especially foot adapted to walking upright. - bones found in "Rising Star" cave in South Africa - closer in appearence to Homo species such as H. erectus than to Australopithecus afarensis. But it possesses enough traits shared with no other member of our genus that it warrants a new species name.

Origin of Multicellularity

- The evolution of eukaryotic cells allowed for a greater range of unicellular forms. - A second wave of diversification occurred when multicellularity evolved and gave rise to algae, plants, fungi, and animals.

Denisovans

- extinct species of archaic hominid and a close relative to modern humans, lived in Serbia and SE Asia - responsible for the EPAS1 allele that allows a group of modern humans from Tibet the ability to live at very high altitudes - interbred with neanderthalensis and homo sapiens - "Mixing" btwn ancient human and Denisovans. Allele preserved in those humans who migrated to high mountains, was lost in lowland population.

Human presence vs animal species

- gradual decline in regions where humans originated from (Africa) - sharp decline in regions that humans later migrated and arrived at (ex: Australia's percent of species declined sharply between 100,000 and 10,000 years ago, North America's percent of species declined sharply 10,000 years ago, and Madagascar and NZ's percent of species declined sharply in between 1,000 and 100 years ago.

Monotremes

- mammalia lineage - Platypus and echidnas, Lay eggs, Have milk, but no nipples)

Eutherians

- mammalia lineage - Canines, felines, rodents, bats, whales, horses, humans, etc..., "Placental mammals", Embryo completes development within the uterus of female

early hominins

- smaller stature - smaller brains - protruding jaws - large teeth

Photosynthesis & Oxygen Revolution

-Most atmospheric oxygen (O2) is of biological origin -O2 produced by oxygenic photosynthesis reacted with dissolved iron and precipitated out to form banded iron formations

Marsupials

-mammalia lineage - Opossums, kangaroos and koalas, Later part of embryonic development is in a maternal pouch [the marsupium], embryos develop in uterus.

Meiosis & Mendel link to Evolution

1) Meiosis shuffles alleles, providing new combinations of traits in offspring 2) We predict the traits of offspring using Mendelian genetics 3) The genetic makeup of a population will remain stable unless acted upon by certain mechanisms of change. 4) These "mechanisms of change" underlie evolution.

evidence for endosymbiotic theory

1. inner membranes of mitochondria and chloroplasts are similar to plasma membranes of prokaryotes 2. Replication is similar in these organelles and some prokaryotes 3. Prokaryotes, mitochondria, and chloroplasts all have circular DNA and transcribe and translate their own DNA 4. Mitochondria and chloroplasts ribosomes are more similar to prokaryotic than eukaryotic ribosomes ex: Pelomyxa palustris (eukaryotic amoeba without mitochondria relies on energy produced by various endosymbionts (both bacteria and archaea species)

Genetic structure

A population's "allele frequency" and "genotype frequency". The "frequency" is the proportion - the relative number - usually expressed as a decimal, e.g., 0.4

Prezygotic barriers

Block fertilization by: - Impeding different species from attempting to mate - Preventing the successful completion of mating - Hindering fertilization if mating is successful Examples: Habitat/ecological isolation, temporal isolation, behavioral isolation, mechanical isolation, gametic isolation,

Homo neanderthalensis

Close, extinct relative to Homo sapien species - lived in Europe and the Near East from 350,000 to 28,000 35,000 years ago -Thick-boned with a larger brain, they buried their dead, and they made hunting tools - Share common ancestor with H. sapiens ± 500,000 y.a. - genomic DNA suggests there was gene flow btwn them and humans. - mitochondrial DNA

Hierarchical classification

Did King Phillip's Children Order Fries, Gravy, and Shakes? (Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species)

General consensus on species

Different species are genetically different from one another.

Habitat differentiation

Factor that can reduce gene flow within one population: a mutation may affect where you live/mate

Pollinator preference

Factor that can reduce gene flow within one population: a new mutation may affect pollinators

Sexual selection

Factor that can reduce gene flow within one population: a new mutation may affects mate choice

Polyploidy

Factor that can reduce gene flow within one population: creation of new chromosome numbers (like 4n) that aren't compatible with parents

Speciation

Lack of gene flow may promote populations' dividing into new species. This needs the end of gene flow

Primates

Mammalian order, includes: Lemurs, lorises, and pottos, tarsiers, and antropoids. - have hands and feet adapted for grasping, and flat nails - A large brain and short jaws - Forward-looking eyes close together on the face, providing depth perception - A fully opposable thumb (in monkeys and apes) - Complex social behavior and parental care

Natural selection

Mechanism of allele frequency change. Differential success in reproduction results in certain alleles being passed to the next generation in greater proportions.

Genetic Drift

Mechanism of allele frequency change. The smaller a sample, the greater the chance of deviation from a predicted result. Describes how allele frequencies fluctuate unpredictably from one generation to the next, and tends to reduce genetic variation through the chance losses of alleles.

Common mechanisms of allele frequency change

Natural selection, Genetic drift, Gene flow

Lobe-finned fish

Originated in the Silurian period (~400 mya) - Rod-shaped bones surrounded by a thick layer of muscle in their pectoral and pelvic fins, which some living lobe-fins use to swim and"walk" underwater across the bottom. three lineages survived: coelacanths, lungfishes, and tetrapods.

Macroevolution

Over time, great differences between lineages can be seen

Postzygotic barriers

Prevent the hybridzygote from developing into a viable, fertile adult due to: - Reduced hybrid viability - Reduced hybrid fertility - Hybrid breakdown Examples: Reduced hybrid viability, reduced hybrid fertility, and hybrid breakdown.

What does genetic variation lead to?

Speciation (sometimes)

Embryology

Species that are related go through very similar early stages of individual development. The genetic/molecular control of laying down the skeletal structure in vertebrates evolved in a common ancestor and is shared among all vertebrates.

Convergent evolution

The evolution of similar features in independent evolutionary lineages due to similar environmental pressures. They do not share a common ancestor, but have encountered the same environmental pressures, and natural selection honed them in similar ways.

Reproductive isolation

The existence of biological factors (barriers) that impede two species from producing viable, fertile offspring. These are genetic differences, not geographic. Reinforces and protects the differences that have built up between different species by preventing gene flow. Can be classified by whether factors act before or after fertilization (aka pre- and postzygotic barriers)

Miller-Urey Experiment

Two scientists attempted to reproduce the condition of the (assumed) earth's primitive ocean's under a reducing atmosphere. They produced some of the key molecules to life (amino acids and nucleotides).

Bottleneck Effect

Type of Genetic Drift: a sudden reduction in population size due to a change in the environment. The resulting gene pool may no longer be reflective of the original population's gene pool. If the population remains small, it may be further affected by genetic drift.

Founder Effect

Type of Genetic Drift: occurs when a few individuals become isolated from a larger population. Allele frequencies in the small founder population can be different from those in the larger parent population.

Evolution

a change in allele frequencies in a population over generations

phylogenetic tree

a graphic representation of the evolutionary relationships between groups

The Biological Species Concept

a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring; they do not breed successfully with other populations

Proximate causation

addresses "how" a behavior occurs or is modified (Tinbergen's 1 and 2)

Arthopods

an invertebrate animal of the large phylum Arthropoda, such as an insect, spider, or crustacean. Most widespread and diverse animal along with tetrapods

Tiktaalik

ancestral lobe-finned fossil, "fishapod", fish and tetrapod characteristics (transitional species).

Osteichthyans

bony fish

Hominin evolution

brain size increase (Homo erectus had a larger brain than early Homo, which in turn had larger brains than those of the australopithecines they shared East African grasslands with. Maximum brain size (and apparently body size) was attained by H. neanderthalensis. Both brain and body size appear to have declined some 10% in recent millenia).

craniates

chordates with a head

Amphibia

class of tetrapod: - Frogs, salamanders, caecilians - Mostly damp habitats - External fertilization - 100s of species going extinct due to pollution, climate change, habitat loss and mortality from a fungus

reptilia

class of tetrapod: - amniotes: have eggs with protective chambers that allow development outside of water, have less permeable skin and lungs ventilated via rib cages - Extant (living) reptiles include turtles, alligators, lizards, snakes and birds - Have scales with keratin - Internal fertilization - Lay shelled eggs - Ectotherms and endotherms

mammalia

class of tetrapod: - amniotes: have eggs with protective chambers that allow development outside of water, have less permeable skin and lungs ventilated via rib cages - Have mammary glands which produce milk for offspring - Have hair - Have differentiated teeth - Endothermic, with high metabolism

Chimpanzee

closest living relatives to Homo sapiens - share 99% of genome with humans - although --- differential expression of regulatory genes affects phenotype in large ways - Genetic differences and the characteristics they code for separate these primates from humans, and humans from them and other primates.

vertebrates

craniates with a backbone

Morphological species concept

defines a species by structural features. It applies to sexual and asexual species but relies on subjective criteria (b/c how many features must they share?)

Sahelanthropus tchadensis

earliest fossil of human lineage ( about 6.5 mya)

Encephalization

early on in animal evolution, the ancestor of bilateral animals evolved this trait - the clustering of sensory organs in the anterior portion of the body (skull, brain, eyes, and other sensory organs)

Hardy-Weinberg equilibrium

equilibrium situation in which allele and genotype frequencies do not change from one generation to the next, so no evolution is occurring for genes at that gene locus.

"Evo-Devo"

evolutionary developmental biology - Compare anatomy of different organisms, discover the underlying genes responsible for development of this anatomy, and find out how these genes change over time to give us the forms we see today

Tetrapods

evolved from lobe-finned fishes around 365 million yrs go, vertebrate animals having four feet, legs or leglike appendages three classes - amphibia, reptilia, mammalian

Stromatolites

first single-celled organisms, 3.5 billion yrs ago

Behavioral ecology

foraging and mating

Arthopods

hard skeleton on outside of body, jointed legs, ex: crustaceans, insects, spiders, centipedes/millipedes

Hox genes

homeobox genes in animals. They provide positional information in animal embryo, especially anterior <—> posterior positioning of body parts. Hox genes are "master control genes". originally discovered by studying animals with mutated genes (homeotic mutants) If genes are expressed, body parts produced in wrong location

Niko Tinbergen

identified four essential questions in animal behavior: 1. What stimulus elicits the behavior, and what physiological mechanisms mediate the response? 2. How does the animal's experience during growth and development influence the response? 3. How does the behavior aid survival and reproduction? 4. What is the behavior's evolutionary history (genetic basis)?

Evolution of vertebrates

influenced by two duplications of Hox genes found in all vertebrate genomes

gnathostomes

jawed vertebrates

Anthropoids

lineage of primates - monkeys and apes, humans too - worldwide distribution

Tarsiers

lineage of primates (eutherians) - live in SE Asia

Lemurs, lorises, and pottos

lineage of primates (eutherians) - live in Madagascar, SE Asia probably resemble the early arboreal primates

Hominins

mammals that have a large brain and bipedal locomotion - reduced canine teeth - relatively flat faces • head held over body

Gene flow

mating and exchanging genes between populations holds the phenotype of a species together. If it happens rampantly between 2 diff species, they will eventually degrade the genetic boundaries btwn them

Recipe for Life

organic molecules + method of replication (RNA) + a container (vesicles, lipids can do this- self-assemble into barrier, ie hydrophilic heads and core and phobic taiils)

endosymbiotic theory

origin of mitochondria and chloroplasts 1) An anaerobic, predatory prokaryotic cell engulfs an aerobic bacterium 2) Descendants of the engulfed bacterium evolve into mitochondria 3) Mitochondria-containing cell engulfs a photosynthetic bacterium 4) Descendants of the photosynthetic bacterium evolve into chloroplasts

Allele frequencies equation

p + q = 1

Hardy-Weinberg Equation

p2 + 2pq + q2 = 1. They will always equal one (because of math). IF the population is in HW equilibrium, then: p2 = freq. of hom. dominants; 2(pq) = freq. of heterozygotes; q2= freq of hom. recessives

Alexander Oparin (Russia) and John B. S. Haldane (England)

prominent figures in 1920s that emerged modern scientific ideas about orgin of life.

homeobox

regulatory gene that affects gene expression. - Particular DNA sequence of 180 nucleotides - codes for the 60-AA "homeodomain" region of protein - genes with homeobox are called homeobox genes (but not all of them regulate body plans) - homeodomain part of that protein allowing it to bind to DNA --> transcription factor!

ancestral chordate

resembled lancelets (no head), but Hox genes expressed anterior of nerve cord

Gene

segment of DNA coding for a protein or other trait

Homologous Structures

structures that have the same evolutionary origin. or also anatomical features shared by a group because they inherited them from a common ancestor. (ex: Forelimbs of tetrapods)

Ecology

study of interactions between organisms and the environment.

What occurs when Hardy-Weinberg equilibrium is not met?

the allele frequency and/or genotype frequency can change from generation to generation. That is, microevolution can occur.

Microevolution

the change in allele frequency in a population over time (not in genetic equilibrium)

Behavior

the nervous system's response to a stimulus and is carried out by the muscular or the hormonal system - intertwined with physiology and subject to natural selection - selected for individual survival and reproductive success

Hybrids

the offspring of crosses between different species (mules are hybrids of horses and donkeys)

Taxonomy

the ordered division and naming of organisms by humans as a means of organizing, naming, and classifying (Carolus Linnaeus is the the Father of this)

Genotype

the particular alleles for a given trait in an individual (e.g., two alleles for blue eyes)

Allele

the particular version of a gene (e.g., eye color gene for blue eyes), may be dominant or recessive; recessive only appear in the individual in the absence of any dominant ones

Allele frequency

the proportion of a certain allele at a given locus within a population

Genotype frequency

the proportion of a given genotype (of 3 possible genotypes in a two-allele system: e.g., two homozygous genotypes and the heterozygote) within a population

Gene pool

the set of all copies of alleles carried by individuals in a population at one time

Fossils and Comparative anatomy

the study/comparison of body structures among different species. gives evidence of descent with modification, reveal similarities in diff. species explained by shared ancestry, reveals evolutionary change during descent from common ancestor.

Bipedalism

trend in hominin evolution - Hominins began to walk long distances on two legs about 1.9 million years ago when hominins were still living in forested areas - More energy-efficient than walking on all fours

Tool use

trend in hominin evolution - The oldest evidence of tool use, cut marks on animal bones, is 3.4 million years old, suggesting tool use originated before the evolution of large brains

Binomial nomenclature

two-part names for species (genus then specific epithet)

Homo sapiens

± 200,000 years old species - appearedin Africa by 195,000 years ago - All living humans are descended from these African ancestors - The oldest fossils of Homo sapiens outside Africa date back about 115,000 years and are from the Middle East - Humans first arrived in the now - Americas sometime before 15,000 years ago, evidence shows earlier than that, about 33,000 years ago - A number of characters distinguish them from other apes: - Upright posture and bipedal locomotion - Larger brains capable of language, symbolic thought, artistic expression, the manufacture and use of complex tools - Reduced jawbones and jaw muscles compared to other primates - Shorter digestive tract