Biology Exam 3

Identify the type of isolating mechanism: Two species of birds sing different songs. Females are only attracted to the song of their own species.

Behavior

Does evolution occur in individuals or populations? What about natural selection?

Natural selection acts on individuals, but only populations evolve

What are the conditions for natural selection?

variation, inheritance, differential survival and reproduction, adaptation

Identify the type of isolating mechanism: Horses and donkeys can mate to produce a mule (hybrid offspring) which lives a long, healthy life, but is unable to mate.

Hybrid infertility

How would you be able to tell if two organisms that looked very similar and lived in the same area were different species?

If organisms were able to mate and produce a viable, fertile offspring

In each example, identify which condition of Hardy-Weinberg is violated: All members of a plant population have true-breeding yellow flowers. In a random event, a single individual has purple flowers.

Mutation

In each example, identify which condition of Hardy-Weinberg is violated: A population of birds have a mixture of small and large beaks. Small beaks allow the birds to eat small seeds, the most common food source for the birds. Birds with small beaks become more common over time.

Natural selection

How would you be able to tell if two organisms that looked very similar and lived in the same area were different species? What about fossils that looked similar and were found in the same area?

No way to tell using biological species concept (have to use other ways)

Can an organism ever be perfectly adapted to its environment? How come?

No. Not all traits are possible—individuals are constrained by their genetics and history (new traits have to come from mutations in the existing genome). Environments are constantly changing. Many traits results in trade-offs (ex: advantage of humans walking on 2 legs, but disadvantage due to back problems)

In each example, identify which condition of Hardy-Weinberg is violated: Female peacocks prefer to mate with male peacocks with larger, more colorful feathers.

Nonrandom mating

Identify the type of natural selection: Plants that are very tall are exposed to more wind. Plants that are short canʼt get as much sunlight. Plants at a middle height are most common.

Stabilizing selection

Identify if the given example is allopatric or sympatric speciation: A population of maggots lay their eggs in hawthorn fruit. Over time, some maggots began laying their eggs exclusively in apples instead, and a new species (the apple maggot) emerged.

Sympatric

Think back to your rock pocket mice lab. How did the dark fur trait first appear in the population living on the lava flow? Why did it become common in the population?

A random mutation in an individual caused it to have dark fur. This mouse passed on this dark fur gene to its offspring. The dark fur gene gave an advantage, and so mice with dark fur were more likely to survive and pass on the dark fur gene. Over time this adaptation became more common in the population.

Identify if the given example is allopatric or sympatric speciation: A population of deer lives in a forest. A highway and a small town is built that splits the habitat in two. Over time, the populations become two different species of deer.

Allopatric

Identify the type of natural selection: Pocket mice on dark lava flow blend in more and arenʼt seen as easily by predators.

Directional selection

Identify the type of natural selection: Black rabbits and white rabbits can camouflage into the white and black rocks in their environment. However, the intermediate gray rabbits cannot camouflage.

Disruptive selection

Identify the type of isolating mechanism: One lizard species lives in the trees, while the other lives on the ground.

Ecological

How do populations that are physically separated become different genetically?

Evolution—mutations, adapt to different environments/roles, genetic drift, etc.

True or False: All mutations result in adaptations.

False. If a mutation results in a new/changed trait, whether it is helpful, harmful, or neutral depends on the environment.

True or False: Natural selection is about survival of the fittest.

False. Itʼs better to think about it as survival of the fit enough (you donʼt need to be the fastest, just fast enough to escape the predator and not be eaten).

True or False: Natural selection gives organisms what they need or want.

False. Natural selection acts regardless of what organisms need or want. An organism cannot choose or change the traits that it inherits. The genes it happens to inherit may or may not be advantageous, either helping the organism to survive and reproduce or not.

True or False: Natural selection is random.

False. Natural selection favors organisms with traits that help them better survive and reproduce.

True or False: All traits are adaptations.

False. Only traits that are advantageous are adaptations. Some traits are neutral (example: eye color in humans)

Identify the type of isolating mechanism: Certain coral species will release eggs and sperm into the water, but only eggs and sperm of the same species will combine.

Gametic incompatibility

In each example, identify which condition of Hardy-Weinberg is violated: Birds from a population on the mainland migrate to an island, where they join a population of the same species.

Gene flow

In each example, identify which condition of Hardy-Weinberg is violated: A population of fish has about equal numbers of white-colored and black-colored fish. Due to disease, a large number of fish are wiped out. Now, the population is about 80% black-colored fish.

Genetic drift

Identify the type of isolating mechanism: One species of rabbit lives in the Arctic, while the other lives in North America.

Geography

What determines the fitness of an organism? How does this relate to evolution?

How successful an organism is at passing on its genes (ability to survive and reproduce). Genes (beneficial traits) that are passed on by organisms that survive become more common in the population, causing a change in allele frequencies.

Identify the type of isolating mechanism: One species of frog mates during the summer, while the other mates during the winter.

Temporal

True or False: Mutations are random.

True. Mutations occur at random in the DNA and then get passed on during DNA replication.

Name three examples as evidence for evolution.

artificial selection, comparative anatomy, embryology, geographic distribution, fossil record