Science Chapter 2

Who came up with the theory of evolution?

Charles Darwin

Who came up with natural selection?

Alfred Wallace

Who developed the Theory of Evolution by natural selection?

Charles Darwin and Alfred Wallace

Define Evolution?

The change in living things over time as certain traits become more common in a population.

What do mutations do?

They introduce new alleles into the gene pool increasing variation.

What does selection pressure cause?

Some organisms to die while others survive, reproduce, and pass on traits

What is competition/ selection pressure?

Where organisms compete for food, space and mates - only some survive.

What does “Survival of the fittest” mean?

The individuals with the best traits for their environment survive longer, and reproduce more

What is meant by “Change in allele frequency”?

How often specific gene versions appear in a population over time.

What is the result of Natural Selection?

The population becomes better suited to its environment.

What 6 words explain Darwin’s theory of evolution by natural selection?

Variation

Competition/ Selection pressure

Survival of the fittest

Survivors reproduce

Change in allele frequency

Population better suits environment

Why do parents have more children than needed to replace themselves?

It increases the chance that some survive environmental pressures and reproduce successfully

What is the first main point of Darwin’s theory?

All forms of life evolved and descended from a single common ancestor through gradual changes.

What is the second main point of Darwin’s theory?

Evolutionary changes happen through natural selection acting on variations within populations over many generations.

Why doesn’t natural selection always reduce variety completely?

Because different traits stay useful in changing environments or conditions.

What is required for natural selection to create Earth’s diversity?

Populations must become isolated and adapt separately under different environmental pressures, leading to new species.

What is divergence evolution?

When two related species develop different traits due to different environmental pressures.

What is convergence?

When unrelated species evolve similar traits because they adapt to comparable environmental conditions.

What is speciation?

The formation of new species from a common ancestor due to isolation and natural selection.

What defines a species?

A group of organisms that can reproduce together to produce fertile offspring capable of further reproduction.

What happens when similar species interbreed?

They can produce hybrids, like ligers, but the offspring are infertile and cannot reproduce further.

What causes variation?

Mutations, random fertilization, and crossing over during meiosis

What is isolation in evolution?

When a population splits and new groups become unable to exchange genes due to barriers.

What is behavioral isolation?

Differences in courtship rituals, mating songs, or behaviors prevent interbreeding between closely related species.

What are fossils?

Preserved remains or traces of ancient organisms embedded in rock from past geological periods.

What is paleontology?

The scientific study of past life through fossil evidence, revealing Earth’s biological and evolutionary history.

What are the main fossil types?

Whole organisms, parts, carbon films, and imprints

What are “whole organism” fossils?

Entire organisms preserved in amber, ice, or tar

What is a carbon film fossil?

A thin carbon outline of an organism left after decay and pressure.

What are imprint fossils?

Preserved surface marks like footprints, shell impressions, or worm trails left in sediment.

What is the first step in fossil formation?

Organisms are rapidly buried in mud, ice, or resin, preventing decomposition and preserving remains.

What is relative dating?

Determines fossil age by comparing rock layers’ positions, with deeper layers being older.

What is absolute dating?

A method that uses radioactive decay to find a fossil’s actual age in years.

What are analogous structures?

Structures with the same function but different structure.

Are analogous structures evidence of a common ancestor?

no but it could be evidence for common selection pressure

What are index fossils?

Widespread species existing briefly in geological time, helping compare ages of rock layers globally.

What is radiometric dating?

Calculates material age using isotope decay into stable products, based on measurable half-life rates.

What is a half-life?

Time required for half of a radioactive isotope’s atoms to decay into stable daughter elements

What are stromatolites?

Layered rock formations created by fossilized bacteria and sediment, proving ancient microbial life existed

How do fossils support evolution?

Fossils show how species slowly changed, appeared, or disappeared over long periods of time.

What do younger fossil layers show compared to older ones?

Younger layers have more complex, varied species; older layers show simpler life forms.

Why are soft-bodied organisms rarely fossilized?

They break down quickly and don’t have hard parts that can turn into fossils.

What information do most fossils provide?

Mostly the outside shape, not the inside organs or how the organism worked.

What can vestigial features include?

Behaviors, body structures, or biochemical processes that lost their original function.

What does embryology show about evolution?

Early embryos of vertebrates look alike, showing shared ancestry.

What does DNA sequence comparison show?

Genetic similarities and differences revealing how species are evolutionarily related.

What does chromosome comparison reveal?

Humans and chimpanzees share very similar DNA content and chromosome patterns.

What do DNA base sequence differences show?

How closely related species are and how long ago they diverged.

What does embryonic development comparison reveal?

Similar growth stages in embryos suggest shared evolutionary origins.

How can antibiotics cause bacterial resistance?

Overuse kills weak bacteria, allowing resistant ones to survive and multiply.

What is MRSA?

A bacteria strain resistant to most antibiotics, making infections hard to treat.

What happens in antibiotic resistance?

Resistant bacteria survive antibiotics and reproduce, spreading resistance genes.

Why are sickle cells harmful?

They block blood flow, causing pain, strokes, and organ damage.