unit 4 biology: evolution :)

evolution

process of biological change by which descendants come to differ from their ancestors

What 4 scientists are important in development of the evolution theory?

Carolus Linnaeus, Georges Louis Leclerc de Buffon, Erasmus Darwin, Jean-Baptiste Lamarack

Carolus Linnaeus

(1700s) developed classification system to name living things (grouped by similarities)

Georges Louis Leclerc de Buffon

(1700s) proposed species shared ancestors instead of arising separately

Erasmus Darwin

Darwin's grandfather (Physician M.D.). Proposed that all living things were descended from a common ancestor

Jean-Baptiste Lamarack

Proposed theory that all organisms evolved toward perfection and complexity

a. proposed changes in environment caused an organism behavior to change

What was the controversy on the Age of Earth?

Religious Belief: Bible claims 6,000 yrs vs The History of Fossils

James Hutton

(late 1700s) proposed that Earth was very old. Said geologic change occurred gradually

Charles Lyell

(1830) published "Principles of Geology". Also said Earth must be very old. Said changes on Earth occurred at constant rate over time

a. Same changes were happening today

b. Greatly affected Darwin's thinking

What did Darwin observe in the Galapagos?

1. Differences between species studied on Galapagos islands- collect birds/reptiles\>taxidermist

2. Notices variations well suited to the animals environment

3. Studies the birds beaks and tortoise shells and said somehow adapt to their surroundings

4 of Darwin's contributions to geologic evidence

1. Discovered fossil evidence of species changed over time

2. Suggested that modern organisms have relationship to fossil forms

3. Earth must be very old (supported Lyell's theory)

4. Darwin said, like the Earth, organisms must change gradually over time

Artificial Selection

process by which human changes a species by breeding it for certain traits

Darwin's idea about breeding

a. compared it to the idea of adaptation

b. Said that in nature, environment creates selective pressure instead of humans in artificial selection

Natural Selection

mechanism by which environment is selective agent

a. Darwin used work of others to develop theory

b. said adaptions arose over many generations (decent with modification)

4 main principles to theory of natural selection

Variation, Overproduction, adaptation, decent with modification

Fitness

measure of ability to survive and produce more offspring relative to other members of a population

What does natural selection act on?

Phenotypes (as environment changes, different traits will become beneficial)

Where did Darwin's evidence for evolution come from?

Fossils, Geography, Embryology, Anatomy

Homologous structure

features that are similar in structure but have different functions (suggested common ancestor)

analogous structure

structures that perform similar function but are not similar in origin (i.e. wings of bats and insects)

vestigal structures

structures or organs that seem to lack any useful function that had a function in early ancestor

Paleontology

study of fossils or extinct organisms

What evidence supports fossil anatomy?

Molecular and genetic evidence

DNA sequence analysis

more closely related have more similar DNA

Pseudogenes

genes that no longer function. Similarities in organisms suggest common ancestor

Protein comparisons

Similarities in proteins found in specific cell type suggest common ancestor

What does genetic variation increase? How?

Survival

a. lead to difference in phenotypes

b. natural selection acts on phenotypes

c. the greater range of phenotypes the more likely individuals can survive with change in environment

Gene pool

genetic variation stored in population

Where does genetic variation come from?

Mutations and Recombination

Mutation

Random Change in organisms DNA

a. can form new allele

b. in reproductive cells can be passed on

c. increases genetic variation in gene pool

Recombination

new allele combination form offspring

a. meiosis

b. crossing over

How does Natural Selection acts on distribution of traits?

1. Normal distribution gives normal "bell" shaped curve
2. Environmental conditions can change and certain phenotypes become an advantage

Microevolution

observable change in allele frequency of a population over time

a. occurs on small scale with single population

What 3 paths can natural selection change distribution of a trait?

Directional, stabilizing, disruptive selection

Directional Selection

causes shift in a populations phenotypic distribution

a. an extreme phenotype that was once rare is now more common (moving mean)

b. mean value of thats shifts in direction of the more advantages phenotype

c. lead to rise in drug-resistant bacteria

Stabilizing Selection

the intermediate phenotype is favored and becomes more common (mean is narrow)

a. decreases genetic diversity

b. extreme phenotypes may be lost

Disruptive Selection

occurs when both extremes are favored and intermediate are selected against (separated mean)

a. can lead to formation of new species

gene flow

movement of alleles from one population to another

How does gene flow affect a population?

a. increases genetic variation

b. keeps gene pool similar

c. less can create genetically different populations

d. lack of it increases chance that two populations will evolve into different species

What are small populations most likely to be affected by?

Chance

Genetic Drift

changes in allele frequencies due to chance

Bottleneck Effect

genetic drift that occurs after an event (i.e. hunting)

Founder Effect

genetic drift that occurs after a small number of individuals colonize an area

What are 2 effects of genetic drift?

1. lose genetic variation: ability to adapt it lessened
2. Lethal alleles: more common due to chance

Sexual Selection

Occurs when certain traits increase mating success

a. certain traits become more exaggerated

Hardy Weinberg equilibrium

describes populations that are not evolving

What are 5 indications of a genotype that stays the same over time?

1. very large populations
2. no emigration or immigration
3. no mutations
4. random mating
5. no natural selection

What is the basic equation of the Hardy Weinberg equilibrium?

p^2+2pq=q^2=1

What are 5 factors that can lead to evolution?

1. Genetic drift
2. Gene flow
3. Mutation
4. Sexual Selection
5. Natural Selection

Speciation

the rise of two or more species from one existing species

Reproductive isolation

when members of different populations can no longer mate successfully with one another

Behavioral Isolation

isolation caused by differences in mating behavior

Geographic Isolation

involves physical barriers that divide populations

Temporal Isolation

Timing prevents reproduction between populations

What does environment control?

direction taken by natural selection

Convergent Evolution

evolution towards similar characteristics in unrelated species

Divergent Evolution

related species evolve in different directions and become increasingly different

Coevolution

two or more species evolve in response to changes in each other

Evolutionary arms race

coevolution can occur in competitive relationships

Extinction

elimination of a species from Earth

Background Extinctions

extinctions that occur continuously at a very low rate

Mass Extinction

more rare, but more intense

a. can occur globally

b. catastrophic events

Punctuated Equilibrium

bursts of evolutionary activity

Adaptive radiation

Diversification of one ancestral species into many descendant species

Permineralization

minerals carried by water are deposited around or replace that hard structure

Natural casts

form when flowing water removes all of original bones, leaving impression in sediment. Minerals fill the mold

Trace fossils

record activity of organism (i.e. nests, burrows, imprints, footprints)

Amber-preserved fossils

organisms trapped in the tree resin that hardens to amber

Preserved remains

from when entire organism becomes encased in material such as ice, volcanic ash, or immersed in bogs

Where do most fossils form?

Sedimentary rock

What percent of living things become fossils?

*tiny*

What provides an accurate estimate of fossil's age?

Radiometric dating

Relative Dating

estimate of date by comparing placement of fossils in rock layers

Radiometric Dating

technique using natural decay rate of unstable isotopes

Radiocarbon dating

Isotope of carbon used with half life of 5700 years


1. organisms consume carbon by eating and breathing
2. When organism dies C14 begins to decay
3. Look at ratio of C14 to C12

How did we determine Earth's age?

* use decay of uranium to determine age (long half-life)


* earth is about 4.6 billion years

Index fossils

another tool to determine the age of rock layers

*Organisms that existed only during specific life spans of time over large geographic areas*

Geologic Time Scale

representation of Earth's history

The three basic units of time

Epochs\>Periods\>Eras

How are eras (last ten to hundreds of million years) separated?

a. periods of mass extinction

b. leads to periods of adaptive radiation

Periods

most common used units. Last tens of millions of years

How was Earth different billions of years ago?

* extremely hot the first 700 million years
* atmosphere formed when cool
* no oxygen at first
* when cooled vapor condensed to rain
* organic compounds formed from inorganic materials once water was present (every organism underwater)

Miller-Urey Experiment

(1953) demonstrated that organic compounds could be made by stimulating conditions on early Earth

Meteorite hypothesis

organic molecules may have arrived on Earth through meteorite or astroid impacts

Iron-sulfide bubbles hypothesis

biological molecules formed in chimneys of hydrothermal vents

Lipid membrane hypotheis

evolution of lipid membranes crucial step for origin of life

a. lipid membrane concealed around organic molecules forming cell-like structures

What is the earliest genetic material?

RNA (can self-replicate)

How did single celled organisms change Earth's surface?

* depositing minerals
* giving of oxygen

How long ago did photosynthetic life evolve?

3.5 Billion years ago

What did higher oxygen levels in the atmosphere allow?

Evolution of aerobic prokaryotes

How have eukaryotic cells evolved?

Endosymbiosis

Endosymbiosis theory

one organism lives within body of another, and both benefit from relationship

What were mitochondria and chloroplasts 1.5 billion years ago?

simple prokaryotic cells taken up by larger prokaryotes

What did the evolution of sexual reproduction lead to?

Diversity

How did the first prokaryotes and eukaryotes reproduce?

asexually