BILD 3 Learning Objectives Final w/ Stockwell

Interpret a histogram.

X-axis is usually scale of trait; y-axis is portion of population that holds that trait

Define the 3 properties of a trait required for it to be subject to evolution by natural selection. For each property, explain why evolution by natural selection would not happen if that property were absent.

1) Inheritance - offspring inherit traits from their parents. Natural selection would be absent without this property because offspring inherit the more desirable traits for the environment from the parents.

2) Variation - individuals within a population have different characteristics/traits. Evolution by natural selection would not happen if this property were absent because in natural selection, desirable traits in a certain environment would be passed down more, since the "fittest" have a higher survival rate. Without a variation of traits, a population could easily disappear or have too many individuals.

3) Competition (Differential survival and reproduction) - more offspring produced than can survive, so offspring with traits better matched to the environment survive and reproduce more effectively than others. Natural selection is literally "survival of the fittest" therefore competition is essential for natural selection.

Explain why natural selection only causes evolution if the trait under selection is at least partly heritable.

The trait must be able to provide a survival/reproductive advantage to offspring

Because as some individuals survive over others, their traits are passed onto their offspring, changing the frequency of those traits within a population

Explain how there can be natural selection without evolution. Explain how there can be evolution without natural selection. Give an example of each process.

Natural selection without evolution happens if traits are not genetically based, so natural selection will have no evolutionary consequence. If the fatter individuals that survive became fat only because of the environment in which they occur (for example, better access to resources), then their offspring will not necessarily be fatter, on average, than the original population

Evolution without natural selection → mutation, genetic drift, gene flow

Given a description of a species, propose some plausible mechanisms that could limit the growth of its population.

Predation

Starvation

Emigration

Habitat loss

Natural disasters

Define evolution.

Evolution by natural selection happens whenever there is variation in a heritable trait that affects survival and/or reproduction

Describe the prevailing view regarding evolution and species in Europe in the 1800s.

- God created each species via "special creation"

- Scholars thought the Earth was a few million years old

- Understood pattern but not process of evolution

Linnaeus

Developed binomial nomenclature that is still used today

- Genus species

- Darwin argued that classification should be based on evolutionary relationships

Hutton

- Earth is a few thousand years old

- Earth's geological features explained by gradual mechanisms → valleys formed by rivers

- Both Hutton and Lyell got Darwin thinking that the Earth was older than people thought.

Lyell

- Slow processes like erosion have always shaped the Earth

- The forces observable today can create what we see around us, given enough time

- Darwin realized Earth must be more than a few thousand years old and that these processes could also induce biological change

Cuvier

- Older the lifeform, more dissimilar its fossils were to current life-forms

- Species are periodically wiped out by catastrophic events, represented by strata

- Between layers of strata, some species appear/disappear

- Denied species ever evolve

Malthus

- Economist that believed much of human suffering resulted from human potential to increase faster than food supplies and other resources

- Darwin extended this idea to all species:

- capacity to over-reproduce was characteristic of all species

- only fraction of born organisms survive long enough to reproduce → must have traits that are better at survivability to be passed on (advantage, not guarantee)

Lamarck

- Use and disuse

- Offspring inherit acquired characteristics of their parents

Describe what nested hierarchical categorization of organisms means, and identify whether or not this type of organizational system is still in use today. Covered only in the reading.

- Adopted by Linnaeus, grouping similar species into increasingly general categories

- Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

- still in use

Define the hypothesis of gradual geologic change, name its proponents, describe its predictions about the age of the Earth, and discuss the evidence to support it that Darwin found on his voyage.

- Hutton proposed Earth's geological features can be explained by gradual mechanisms

- Earth much older than a few thousand years

- Earthquake in Chile → rocks along coast shifted (found fossil marine shells in sedimentary rocks at 12,000 ft.)

Explain Lamarckian evolution, and be able to give an example of how this mechanism was hypothesized to lead to change. Evaluate Lamarck's views in light of current biological knowledge. Covered only in the reading.

- Proposed incorrect mechanism for evolution

- "Use and disuse" - parts of body that are used grow larger, those that are not used deteriorate; ex. Giraffe stretching neck to reach leaves on high branches

- Believed that evolution occurs because organisms have an innate drive to become more complex

- "Inheritance of acquired characteristics" - organisms can pass on these modifications to their offspring; muscular neck of living giraffe passed onto generations

Describe the biogeographical patterns Darwin observed on his voyage and explain how they provide support for the theory of evolution.

- Discovered fossils in cliffs

- Fossils + earthquake that shifted coast shelf by eight feet

- Different islands within archipelago supported different species and subspecies

- All species are related by descent with modification from a common ancestor

- If Earth is old, must have been enough time for several branches to occur

Explain the principle of succession and why it constitutes evidence for descent with modification.

- Living organisms are similar to fossils in their region because they are descendants from those ancestors

- Ex. Australian fossils are similar to Australian living mammals

Describe the process of artificial selection, compare it to natural selection, and explain why it contributed to Darwin's understanding of evolution.

- Humans modify other species by selecting which traits are desired

- Darwin extended these ideas to natural selection / evolution

- Natural selection is controlled/impacted by the environment and habitat

- Natural selection similarly selects and breeds individuals with desired traits, specifically for survival and reproduction

Give some examples of how organisms have colonized new habitats via dispersal.

- Animals and plants disperse on their own

- Fed seeds to sparrow → fed sparrow to hawk → hawk poop can grow plants

- Clams travel by beetle

- Vegetation rafts

Describe the process of adaptive radiation that led to many Galapagos finches with different beaks. Explain how local adaptation and character displacement can each contribute to increased differences between populations. Explain why character displacement requires competition between two populations, and describe its effects on the character (trait) under selection.

- Darwin's finches rapidly diversified from their ancestral species to have a multitude of new beak forms; a change in the environment made new resources available (food), created new challenges, or opened new environmental niches

- Led to ideas on adaptive radiation

- Discovered huge variation in bill size and shape

- Adaptive radiation - the diversification of species originating from a common ancestor to fill a wide variety of ecological niches ( habitat is your address, ecological niche is your profession)

Character displacement - process of evolutionary divergence of coexisting species (no overlap anymore)

The phenomenon where differences among similar species whose distributions overlap geographically are accentuated in regions where the species co-occur, but are minimized or lost where the species' distributions do not overlap

2 processes leading to divergence and adaptive radiation

Local adaptation

Character displacement

Describe the two main ideas in Darwin's Origin of Species.

Descent with modification - passing traits from parent to offspring

Natural selection - survival of the fittest

Discuss the response to the publication of The Origin of Species: which ideas were rapidly accepted, which were not, and why.

- Within a decade, his book and its proponents had convinced most scientist's that life's diversity is the product of evolution.

- Descent with modification was widely, readily accepted.

Natural Selection was not because it rejected religion.-

Identify the later knowledge that helped garner widespread support for natural selection within the scientific community.

- Better understanding that the earth is really old

- Discovery of radioactivity and radiometric dating ( of rocks )

- Current estimates : earth is 4.6 billion years old

- Better understanding to genetics

- Precambrian age → all underwater, no living mammals

Provide examples of various different types of evidence for evolution, and how each of these is used to demonstrate the occurrence of evolution.

- Fossils usually found in sediment

- Allows us to determine where fossils will be found

- Shows descent with modification

- vestigial structures

- homologous structures

- direct observation

Differentiate between microevolution and macroevolution. Which type of evolution was Darwin thinking about when he described descent with modification?

Microevolution - evolution on short time scales across several generations.

Macroevolution - when major trait changes occur and new species form.

Microevolution + millions of years = macroevolution.

Darwin was thinking of macroevolution when describing descent with modification.

Explain the principle of stratigraphy and how it results from the process of how sedimentary rock and fossils are formed.

older fossils are buried under deeper layers than younger fossils (usually found nearer to the surface)

There has been time for sedimentary layers to build upon the older fossils. Plant and animal remains in the sediment become fossilized.

Explain how the fossil record provides evidence for evolution (including how it demonstrates extinction, succession, and transitional forms).

- We are able to observe descent with modification → species evolving over time into other, similar species

- Extinction - some species disappear between layers of fossil (Irish Elk)

- Succession - living organisms are similar to fossils in their region because they are descended from those ancestors with modification

- Transitional forms - provide evidence of intermediates between different modern day and extinct forms. If you find fossils that are different from extant species, then you know it went extinct

Describe the hypothesis that Tiktaalik's discoverers were testing when they searched for a transitional tetrapod in 375 million year old rocks.

Hypothesis: if you want to find a transitional fossil, you should look into rocks that are within 365 million to 385 million years ago (descent with modification)

Tiktaalik was found in 375 million year old rocks

Prediction: If you've taken these rocks, you'll find a combination of the fish and tetrapod

List the main ways in which Tiktaalik resembles modern tetrapods.

- flat head

- eyes on top

- ribs

- neck

List the main ways in which Tiktaalik resembles fish.

- specialized fins (however, they're fins with wrist; fish had fins)

- scales

Be able to explain why transitional fossils are not necessarily direct ancestors of modern organisms, but rather cousin-like. How does this relate to the "shape" of the tree of evolution (i.e. is it a straight ladder, or a tree with many branches)?

Transitional fossils are intermediates between extinct and modern day forms. Therefore, it's possible that the transitional fossils were on a branch that broke off the modern organisms and were formed later.

The shape of the tree of evolution has many branches.

List some vestigial structures in humans and the functions they served in our ancestors.

- Goosebumps (hairs on our forearms and legs) → traps air for thermoregulation, defence (standing hair makes the individual look bigger)

- Wisdom teeth → masticate tough, raw foods

- Appendix → digest tough, raw foods

- Tailbone/tails → balance, brushing away insects, grasping things

Define homology.

Homology - trait that two species share because both inherited it from a common ancestor

Explain how molecular homology can reveal common evolutionary origins.

- similarity among organisms at molecular level (genetic code)

Genetic code: in nearly all organisms, the same codons (nucleotide triplets) specify the same amino acids

Shows that this process is truly ancient if all living beings have this

Explain how structural homology can reveal common evolutionary origins.

- tetrapod forelimbs have the same basic structure despite different function because of modifications of ancestral form

Explain how developmental homology can reveal common evolutionary origins.

- inherited similarities during development, despite differences in adults (vertebrate embryos)

- Chicken and human embryo very similar but change drastically after birth

Compare and contrast homology, vestigial structures, and convergent evolution (analogous structures). Be able to give an example of each.

- Homology - a trait shared between 2 species because both species inherited it from a common ancestor; Ex. tetrapod forelimbs

- Vestigial structures - remnants of features that served a function in the organism's ancestors; ex. Appendix in humans, mexican tetra vs blind cave tetra

- Analogous structures - organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments; insect wings vs bird wings

Be able to give examples of evolution occurring in the modern day.

Overuse of insecticides causing the development of resistance in insects

Using evolutionary reasoning, justify the fact that much of the National Institutes of Health budget is devoted to research on non-human organisms.

- Homologous anatomy within mice, frogs, rats, and humans

- Since we are molecularly homologous with other organisms, given by the idea that we descended from common ancestors, testing on non-human organisms and their reaction can give clues to how humans will react to similar drugs or situations.

Hardy-Weinberg Equilibrium

A mathematical null model that predicts no change in genotype or allele frequencies in a population under certain conditions.

- Essentially, it is a description of what the gene pool looks like in the absence of evolution.

Locus

particular location on a chromosome

Allele frequency

the relative frequency of an allele at a particular locus in a population, expressed as a fraction or percentage

Genotype frequency

the number of individuals with a given genotype divided by the total number of individuals in the population

- frequency or proportion of genotypes in a population

Genetic drift

random allele frequency changes due to chance; decreases variation; only visible in smaller populations

Gene flow

the transfer of alleles into or out of a population due to the movement of fertile individuals and their gametes

- incoming = immigration,

- outgoing = emigration;

- decreases variation between two populations (decrease speciation)

Non-random mating

when the probability that two individuals in a population will mate is not the same for all possible pairs of individuals

- artificial selection; sexual selection, inbreeding (the mating of closely related individuals, as cousins, sire-daughter,brother-sister, or self-fertilized plants)

- can produce excess homozygotes or heterozygotes

Assortative mating

like mates with like

Disassortative mating

like mates with unlike

Explain why we test for HWE.

Determine if population is evolving by looking at gene pool to see if allele frequencies are changing due to certain processes.

Calculate observed genotype frequencies and allele frequencies.

Genotype frequency = # of individuals with genotype of interest / total number of individuals in population

- (#of TT) / total # of genotypes

Allele frequency = # of alleles of interest / total number of alleles

- 2(#ofTT) + #ofTt = (total T) / total # of alleles

Calculate the expected genotype frequencies and genotype counts under HWE. Compare these with observed genotype frequencies/counts. Use the results to evaluate whether a population is in HWE.

Expected genotype frequency:

TT = p^2 * (#of individuals)

Tt = 2pq * (#of individuals)

tt = q^2 * (#of individuals)

If observed = expected, HWE applies

List the 5 conditions that must be met for a locus in a population to be at HWE (i.e., the assumptions of HWE).

1. No mutations - the gene pool is modified if mutations occur or if entire genes are deleted or duplicated

2. Random mating - if individuals mate within a subset of the population, such as near neighbors or close relatives (inbreeding), random mixing of gametes does not occur and genotype frequencies change

3. No natural selection - allele frequencies change when individuals with different genotypes show consistent differences in their survival or reproductive success

4. Extremely large population size - in small populations, allele frequencies fluctuate by chance over time (a process called genetic drift)

5. No gene flow - by moving alleles into or out of populations gene flow can alter allele frequencies

Apply the HWE null model to provide evidence and justification about whether or not a population is evolving / mating non-randomly. If its genotype frequencies are not in HWE, offer plausible explanations of how it is evolving/mating non-randomly (ie which condition(s) of HWE are not met) that are consistent with the data.

Processes that violate the assumptions of HWE: mutation, natural selection, non-random mating, gene flow, genetic drift

Compare and contrast genetic drift and gene flow in terms of their impacts on allele and genotype frequencies in populations and their implications for future genetic variation in a population.

Genetic drift - change in genetic composition of population caused by random sampling

- effects are only noticeable in one generation if the population is very small

- fixation of an allele: all members of the population have the same allele of a particular gene

Gene flow - movement of individuals or alleles from one population to another

- Reduces genetic differences among populations

- Counteracts loss of genetic variation caused by genetic drift

Explain how genetic drift is a result of sampling effects in finite populations. Explain the main consequences of genetic drift for populations and how the intensity of those effects depends on population size.

Easy for trait to dominate in population over several generations, but only noticeable in one generation if population is very small because there are less possible states

In large population, variation is much higher to start with and will take a long time for one to completely fixate because allele frequency will keep fluctuating.

Describe two ways that populations can become abruptly smaller, intensifying the effect of genetic drift. Explain how this can affect allele frequencies in the smaller populations.

Founder effect - small number of individuals start a new population

- Gene frequencies of new populations are different from the source population by chance

Bottlenecking effect - sudden change that drastically and randomly reduces the population size

- Changes allele frequencies by chance

Compare and contrast selection, mutation, drift, and gene flow in terms of their ability to change allele and genotype frequencies in populations, and their relative strengths in large and small populations.

Selection : large impact

- Assortative mating: if the population being studied actually consist of two subpopulations and most mating occurs within subpopulations, this can produce excess homozygotes

- Disassortative mating: choosing dissimilar mates produces a population with extra heterozygotes

Mutation: small impact

- Changes the allele frequency of the population but its effect is a small and very gradual change for it to be considered a large influence in changing the allele frequency of the population

- Needs a lot of time before the population's genotype frequencies change

Genetic drift: happens in every generation in every population

- Is stronger/faster in small populations

- Reduces genetic variation over time as alleles are fixed

- Changes allele frequencies at random

- Can interfere with selection, which changes allele frequencies in a consistent direction

Gene flow:

- Reduces genetic differences in populations

- Can counteract the loss of genetic variation caused by drift

- Can oppose natural selection and adaptation by bringing a nonadapted alleles

Contrast genotype and phenotype. Explain why not all phenotypic variation is inherited. Be able to give an example of non-heritable phenotypic variation

Phenotypes: Characteristics of an organism as a result of genes and environment

Genotype: Genetic composition of an organism

-Ex) Bodybuilders alter their phenotypes, but do not pass on their huge muscles-- generation

Describe the lessons learned from the rock pocket mice studies. Covered in the video/quiz

- Dark-colored rock pocket mice first appear in a population of light-colored rock pocket mice because of a genetic mutation that affects their fur color

- Dark-colored rock pocket mice on dark lava flows have white bellies because there's no selection for dark bellies by visual predators

- If dark-colored rock pocket mice had a competitive advantage of 0.1%, it would take more than 1,000 years for 95% of the population to have dark fur

- Natural selection can favor some mutations and not others.

- Selection can change depending on the environment.

- Mutations for advantageous traits are more likely to be passed on to the next generation

- There are at least two genes involved in creating dark-colored mouse fur.

- Dark fur color evolved independently on each lava flow.

- Under similar conditions, natural selection can favor similar adaptations.

Explain what fitness is.

Relative Fitness: the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals

Given an example of natural selection, be able to identify the trait under selection, whether the trait is heritable, and how fitness changes in the given environment. Be able to predict the outcomes of evolution via natural selection.

Moths with multiple body colors can survive better since they can conceal meaning better fitness

- wing color under selection and heritable

- frequency of trait will increase over time

Given a population histogram with a trait shown on the horizontal axis and a description of how natural selection acts on the trait, sketch a histogram showing how the population will change after natural selection. If the trait is heritable, sketch the histogram of how the population will likely look in subsequent generations. (This was also partly covered in the "Overview of evolution by natural selection" lectures about a hypothetical rabbit population earlier in the class.)

Compare and contrast the 3 modes of natural selection covered in class (directional, stabilizing, disruptive) with regards to which phenotypes are most fit, how the population mean changes as a result of selection, and how genotypic and phenotypic variation change as a result of selection. For each mode of selection, be able to sketch the fitness curve and explain what it means; and generate a graph of how phenotypes change over time. Given a scenario or graph of how natural selection affects a population, infer which mode of selection is at work and predict the long-term consequences of the selection.

Directional Stabilization: Favors individuals with one extreme phenotype

- Population variation decreases and pop. mean changes

Stabilizing Selection: Favor intermediate phenotypes and acts against both extremes

- Population variation decreases and mean stays the same

Disruptive Selection: Favors both extremes

- Population variation increases and mean stays the same

Explain how balancing selection maintains genetic variation. Give examples of two kinds of balancing selection.

Includes heterozygote advantage and frequency-dependent selection.

Maintains polymorphism in the natural selection

- Heterozygote Advantage: heterozygotes have increased fitness over both homozygotes

- Individuals who are carriers for the sickle cell allele (heterozygotes) are spared the worst effects of malaria yet do not have full blown sickle cell disease.

- Frequency-Dependent: the fitness of a phenotype depends on how common it is in the population

- Scale-eating fish are either left or right mouthed. left attacks right side and right attacks left side. Prey fish guard against whatever phenotype is most common in the lake. From year to year selection favors whatever mouth phenotype is least common.

Why can't natural selection fashion perfect organisms?

1. Selection can act only on existing variations

2. Evolution is limited by historical constraints

3. Adaptions are often compromises

4. Chance, natural selection, and the environment interact

Identify the typical results of sexual selection. Give two different types of sexual selection and give an example of each one

Intrasexual selection

- individuals of one sex (typically males) evolve traits that enable them to compete with other individuals of the same sex to win mating opportunities

- ex: single male may patrol a group of females and prevent other males from mating with them

Intersexual selection

- individuals of one sex evolve traits (physical and behavioral) that are preferred by members of the opposite sex (typically females)

- ex: bright plumage in male birds

Explain why phylogenetic trees are hypotheses

- We don't know 100% if these phylogenetic trees are accurate because most are formed on the assumption of which possibility was most likely to occur

- Derived by traits to see which was most common ancestor but doesn't take in account less likely possibilities like convergent evolution or mutations unless other information already known

Node

represents the common ancestor of two lineages. >2 branches from one node is a polytomy

Taxon

(plural: taxa): A named level in the hierarchy.

Sister Taxa

share an immediate common ancestor and are each other's closest relatives on the tree.

Root

most trees are rooted to an unlabeled branch that

corresponds to the common ancestor for all of the species in the tree

- the most recent common ancestor of all the taxa shown

Lineage

evolutionary history

Character/trait

genotype/phenotype

Character transition

introduction of new trait in offspring that wasn't visible in immediate common ancestor

Phylogenetic tree branch length

may or may not be informative

Biological Species Concept (BSC)

a species is a group whose members have the potential to interbreed in nature and produce fertile, viable offspring

Morphological species concept

-traits are defined by morphological traits alone

-used by paleontologists to define fossils

Ecological species concept

A definition of species in terms of ecological niche, the sum of how members of the species interact with the nonliving and living parts of their environment

List prezygotic barriers to reproduction between populations and give an example of each.

-Physical (barrier, snapping shrimp in isthmus of Panama)

- Habitat (cheetahs and lions are found in same physical location, but lions hunt at night and cheetahs hunt during day, or bugs may live in the same physical habitat but one lives in leaf litter and another may live in treetops)

- Temporal (time of mating seasons are very different --> use environment so differently that they don't interact much). For example the American toad and the Fowler's toad. These are closely related species, but the American toad mates in the early part of summer, while the Fowler's toad mates later in the season.

- Behavioral (how you act). For example lacewings. Males and females sing to each other and only respond to similar sounding songs

-Mechanical (can't physically mate/ can't fit together) For example reproductive parts will only align if the male and female belong to the same species. If they belong to two different species, their reproductive parts will not align, and as a result, these species will not be able to mate

- Gametic isolation (biochemistry doesn't match up to form gamete)

List postzygotic barriers to reproduction between populations and give an example of each.

- Hybrid infertility (unable to mate and produce offspring). For example a mule, the offspring of a donkey and a horse are always sterile)

- Low hybrid viability (not born healthy, so the chance of them dying before reaching reproductive age is high). For example when a puma and ocelot mate and reproduce, the hybrid cannot be sustained by the milk that the mother produces. Genes of the parent species may interact in ways that impair the hybrid's development

Allopatric speciation

The formation of a new species as a result of an ancestral population's becoming isolated by a geographic barrier.

Sympatric speciation

The formation of new species in populations that live in the same geographic area

Give one mechanism of sympatric speciation and an example of it.

Polyploidy:

- condition of having more than two full sets of chromosomes

- the diploid eggs and sperm may or may not combine effectively with the haploid, 1n, eggs and sperm from the parental species

- tetraploid plants and the diploid species from which they came cannot produce fertile offspring together, we consider them two separate species

Based on how fit the hybrids are and how much migration there is in the parent populations, predict the outcome of a hybrid zone

- Reinforcement: hybrids are often less fit than members of their parent species. Natural selection strengthens prezygotic barriers to reproduction, reducing the formation of unfit hybrids

- Fusion: barriers to reproduction may be weak when two species meet in a hybrid zone. So much gene flow may occur that reproductive barriers weaken and the gene pools of two different species become increasingly alike. Two hybridizing species fuse into a single species. For example Cichlids in polluted and murky water cannot see the coloration difference between males, producing many hybrids and leading to the fusion of parent species

- Stability: in many hybrid zones hybrids continue to be produced because they survive or reproduce better than members of either parent species

Define half-life

A half-life is the amount of time after which half the parent isotope atoms will have decayed into the daughter isotope

Explain how measuring the amount of parent and daughter isotope tells us how long it has been since the "clock" started in that sample.

radioactive parent isotope decays into a daughter isotope at a characteristic rate. So the more daughter isotope there is, the less parent isotope there will be. As time goes on, there will be less and less of the parent isotope.

Given the half-life of a radioactive isotope, you should be able to roughly estimate how much of it would be left after a given number of half-lives.

A half-life is the amount of time after which half the parent isotope atoms will have decayed into the daughter isotope.

Explain how carbon in the atmosphere sets the carbon-14/carbon-12 ratio during an organism's lifetime.

A living organism contains carbon 12 and carbon 14. When the organism dies, it stops accumulating carbon and the amount of carbon 12 in its tissues remains constant. The carbon 14 that it contains at the time of death slowly decays into nitrogen 14. By measuring the proportion of carbon 14 to carbon 12 we can determine the fossil's age

Provide the rough time scales and know what kinds of samples for which carbon-14 dating vs. uranium dating are appropriate.

- carbon 14: 75,000 years is the oldest we can measure with carbon dating, so carbon dating is useful for recent organic things

- uranium dating is used for dating much older things, such as lava (500 million

Identify what starts the "clock" for carbon-14 vs. uranium dating samples.

- Carbon 14: when an organism dies

- Uranium: when lava hardens

Origin of life

3.5 BYA

Stromatolites: photosynthetic cyanobacteria found ~3.5 bya that persist today.

- Greatly changed the composition of gases in the atmosphere

- Increased oxygen levels in the atmosphere, leading to the greatest extinction

- Paved the way for oxygen breathing organisms to evolve

Cause, effect, and evidence for increasing oxygen in the atmosphere.

- Cause: cyanobacteria (blue green algae) that photosynthesize

- Effect: largest extinction. Increased oxygen concentrations in atmosphere caused many organisms to die because they were not used to oxygen

- Evidence: Stromatolites (layered rocks that form when certain prokaryotes bind thin films of sediment together)

Endosymbiosis and the origin of eukaryotes. Be able to explain the process of endosymbiosis and list several lines of evidence for this explanation of the origin of eukaryotic cells

- Endosymbiosis hypothesis: a cell engulfed a bacterium and became its host. As a result the engulfed bacterium became a mitochondria inside a eukaryote (mutually useful relationship)

- Later, a eukaryote engulfed a cyanobacteria. Result: chloroplast

First evidence of multicellular life.

- Fossils of multicellular eukaryotes 1.3-1.5 BYA

- Multicellularity = organism has cells that have specialized functions

Explain why the Cambrian "explosion" was important in animal evolution, give the rough date for it, and discuss reasons why so many animal phyla appeared in the

fossil record over the comparatively short time of 20 million years.

- 542 MYA

- First appearance of many extant animal phyla (big group of species that are distinguished by broad characteristics- having a backbone and head)

- More complicated body structures --> eyes, shells, armor, jaws, spines (evidence of predation)

Colonization of land by plants

- Paleozoic Era

- Ordovician

Evolution of terrestrial vascular plants (list the adaptations that allowed them to survive out of the water)

- Paleozoic Era

- Silurian period (plants had to retain liquid- not dry out, circulate water/liquid throughout bodying have structural support) - rigid cell wall

Colonization of land by arthropods

- Paleozoic Era

- Early Devonian