Variation & Mutation
What is the random change in genetic material that can introduce a new version of a trait?
Mutation
What is the process called when individuals with helpful heritable traits are more likely to survive and reproduce?
Natural selection
What is a fossil?
Preserved evidence of past life (bones, shells, footprints, etc.)
What is a species?
Group that can reproduce and produce fertile offspring
Give one human activity that can increase extinction rates.
Habitat destruction (or pollution, overhunting, invasive species, etc.)
Name three sources of variation in heritable traits.
Mutations; mixing of genes during sexual reproduction; passing of different gene versions from parents to offspring
List two environmental pressures that can cause natural selection.
Predators, disease, competition for food/water/shelter, temperature, pollution, habitat changes, human-made chemicals
Name three types of fossils or fossil evidence.
Bones, shells, teeth, footprints, burrows, impressions, traces of activity
What does reproductive isolation mean? Give one example cause.
Populations no longer successfully mate to produce fertile offspring; example cause: geographic separation.
Explain how improper use of antibiotics can influence evolution in bacteria.
Overuse selects for bacteria already less affected → antibiotics kill susceptible bacteria → resistant survive and reproduce → resistance rises
Explain the difference between an inherited trait and an acquired trait; give one example of each.
Inherited = genetic (e.g., beak shape at birth) Acquired = develops during lifetime (e.g., damaged beak)
Why don’t organisms “adapt because they need to”? Provide the correct reasoning.
Mutations are random; selection acts on existing variation — organisms do not change traits intentionally
How can undisturbed rock layers help determine the relative ages of fossils?
Deeper = older, higher = younger in undisturbed layers; law of superposition
List three ways reproductive isolation can occur.
Geographic separation; different mating behaviors; different breeding seasons; physical differences; different habitats; genetic differences
Define "mass extinction" and name one human-caused factor that could contribute to a current increase in extinction rates.
Mass extinction = many species become extinct in relatively short geologic time; human-caused factor: habitat destruction or climate change
Describe how a single mutation could be neutral in one environment but helpful in another. Give an example.
Effect depends on environment (e.g., dark fur mutation helpful in dark environment, neutral in mixed environment)
Using the step pattern for explaining natural selection from the guide, outline how antibiotic resistance can increase in a bacterial population.
(1) Variation exists; (2) some bacteria already resistant; (3) antibiotic is selection pressure; (4) resistant survive and reproduce; (5) resistance becomes more common
Describe two pieces of fossil or anatomical evidence that support whale evolution from land mammals.
Transitional skeletons with aquatic features; reduced hind-limb structures; embryonic similarities
When reading a phylogenetic tree, what does a branching point (node) represent?
A common ancestor
Describe how humans can intentionally change which traits become more common in a species.
Selective breeding: humans breed plants/animals for desired traits (e.g., crops with larger fruit)
A population of plants has individuals with red, pink, and white flowers. A change in pollinators favors red flowers. Explain how gene version frequency could change over generations to make red flowers more common.
Gene version for red flower provides advantage via pollinator preference → individuals with that gene version reproduce more → that gene version frequency rises over generations
Natural selection occurs when (list 5 conditions):
Individuals in a population have variation.
Some variations are heritable.
Environmental pressures make survival or reproduction more difficult for some individuals.
Individuals with advantageous traits leave more offspring.
Helpful traits become more common in the population over many generations.
You find similar bone structures in two species and transitional fossils in rock layers between them. Explain how you would use these data to infer common ancestry (include mention of branching points or nodes).
Similar structures + transitional fossils + relative positions in strata imply descent from a common ancestor; node = common ancestor on tree.
Two populations of the same species become separated for thousands of years and evolve different mating behaviors and genetics. Explain how these changes could lead to speciation.
Separation prevents gene flow (reproduction) → different selective pressures/mutations accumulate → reproductive isolation develops → populations no longer interbreed = new species
Write a short evidence-based argument explaining how rapid environmental change caused by humans can increase extinction rates, and name two specific human actions that contribute.
Rapid change reduces ability of populations to adapt; species with low variation or slow reproduction cannot keep up. Human actions: habitat destruction, climate change, pollution, overhunting, invasive species.