evolution unit test

darwins theory

Natural Selection: Organisms with traits better suited to their environment survive and reproduce more. Over time, those traits become more common in the population.

Explain evolution of a trait using 4 steps of natural selection:

variation, competition, survival advantage, reproduction

weaknesses in darwin’s theory

didnt know about genes and dna, couldnt explain varation, and slow to explain sudden changes

where did darwin make these observations

galapagos islands

lamarcks theory

Use and Disuse – If you use a body part a lot, it gets stronger. If you don’t, it shrinks or disappears.

Inheritance of Acquired Traits – Traits you get during your life can be passed on to your kids.

Explain evolution of a trait using Lamarck’s theory (giraffes)

• Giraffes stretch their necks to reach high leaves.

• Their necks get longer from stretching.

• They pass on those longer necks to their babies.

• Over generations, giraffes have super long necks

modern theory of evolution

based on the recognition that it is POPULATIONS that evolve, not individuals.

population

A group of the same species living in the same area that can interbreed.

gene pool

All the genes and variations (alleles) in that population.

biogeography

The study of where species live now and where their ancestors lived.

How & where do most fossils form?

Fossils usually form in sedimentary rock (like mud or sand) where dead organisms are buried quickly

relative dating

Fossils are dated based on layer order

absolute dating

Uses radioactive decay (like carbon-14 or uranium) to find the actual age in years.

limits of fossil record

• Fossils don’t form for all organisms (soft stuff decays).

• Most are missing, destroyed, or undiscovered.

• Doesn’t show every step — we’re often piecing together a puzzle with gaps.

homologous structures

same structure different function

analogous structures

same structure different function

vestigial structures

Leftover body parts that once had a function but don’t anymore. ex appendix

How can a DNA sequence of a gene be used to determine the relatedness of two species?

Compare gene sequences — the more similar, the more closely related.

What are pseudogenes?

Genes that used to work but are now "turned off" by mutations.

How can amino acid sequences be used to determine the relatedness of two species?

If two species have similar amino acid sequences, their DNA is also similar.

How can embryology be used to determine the relatedness between two species?

Early embryos of different species often look super similar, showing they came from a common ancestor.

georges cuvier

• Developed the theory of catastrophism.

• Studied fossils and established extinction as a fact.

• Believed species did not change over time; they were wiped out and replaced.

thomas malthus

• Wrote about population growth and limited resources.

• Proposed that more individuals are born than can survive, leading to competition.

• Inspired Darwin’s concept of natural selection.

charles lyell

• Developed the theory of uniformitarianism.

• Proposed that Earth changes slowly over long periods through natural processes.

• Supported the idea that Earth was old enough for evolution to occur.

jean baptiste de lamarck

• Proposed that organisms change over time through use and disuse of traits.

• Believed acquired traits could be passed on to offspring (incorrect).

• First to propose a full theory of evolution.

charles darwin

• Developed the theory of natural selection.

• Argued that species evolve over time due to variation, competition, and survival of the fittest.

• Published "On the Origin of Species."

alfred wallace

• Independently developed a theory of natural selection similar to Darwin’s.

• His work encouraged Darwin to publish his own theory.

• Studied species in Southeast Asia.

james hutton

• Founder of modern geology.

• Proposed gradualism: Earth’s geological features formed slowly over time.

• Suggested Earth was ancient, supporting time needed for evolution.

What are the "Five Fingers of Evolution"?

Small population (genetic drift), nonrandom mating (sexual selection), mutations, gene flow, and natural selection.

What is genetic drift?

A random change in allele frequency, especially in small populations.

What is the Bottleneck Effect?

A sharp reduction in population size due to environmental events, leading to less genetic diversity.

What is the Founder Effect?

When a new population is started by a small group, leading to limited genetic variation.

What is gene flow?

The transfer of genes between populations through migration.

What are mutations?

Random changes in DNA that create genetic variation.

What is sexual selection?

A type of natural selection where traits increase mating success.

What is intrasexual selection?

Competition within the same sex (usually males fighting males).

What is sexual dimorphism?

Differences in appearance between males and females of a species.

What is artificial selection?

Humans selectively breeding organisms for desired traits.

What is natural selection?

Organisms with traits better suited to the environment survive and reproduce.

What is directional selection?

Favors one extreme trait (e.g., only the tallest survive).

What is stabilizing selection?

Favors the average trait (e.g., medium size = best chance).

What is disruptive selection?

Favors both extremes (e.g., very small and very large survive, not average).

What is a behavioral adaptation?

An action animals do to survive (e.g., migration, playing dead).

What is a physiological adaptation?

Internal body processes that help survival (e.g., venom, hibernation).

What is a structural adaptation?

Physical features that aid survival (e.g., claws, camouflage).

What is Batesian mimicry?

A harmless species mimics a harmful one.

What is Müllerian mimicry?

Two harmful species evolve to look alike for shared protection.

Allopatric Speciation

A type of speciation where a population is separated by a geographic barrier

Sympatric Speciation

A type of speciation where new species evolve from a common ancestor while living in the same area.

Pre-zygotic Mechanisms

Reproductive barriers that prevent fertilization such as behavioral differences or physical incompatibility.

Post-zygotic Mechanisms

Barriers that occur after fertilization

Adaptive Radiation

Rapid evolution of many species from a common ancestor to fill different ecological roles.

Divergent Evolution

When related species become more different over time

Convergent Evolution

When unrelated species evolve similar traits because they live in similar environments.

Parallel Evolution

Similar traits evolve independently in related species that were separated but faced similar environments.

Coevolution

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

Punctuated Equilibrium

Theory that evolution happens in quick bursts followed by long periods of little change.

Gradualism

Theory that evolution occurs slowly and steadily over time.