Evolution
Question: What is the process by which organisms change over time to adapt to their environment?
Answer: What is evolution?
Scenario: Fossils of a species are found in deeper rock layers and show simpler body structures than similar fossils found in higher layers.
Question: What does this pattern suggest about how the species changed over time? Deeper rock layers are old or young? Higher rock layers are old or young?
Answer: It suggests the species evolved over time, becoming more complex. Deeper layers are older, so the fossil record shows gradual change.
In Linneaus classification model, what two levels form the scientific name of an organism?
Genus and species
Scenario: In a population of beetles, some are green and some are brown. Birds can easily see the green beetles on dark tree bark.
Question: Why is variation in this population important for survival?
Answer: Variation allows some individuals (brown beetles) to survive better in the environment. Without variation, the entire population might be wiped out.
Scenario: Bacteria exposed to antibiotics begin to survive and reproduce even in the presence of the drug.
Question: How is this an example of evolution?
Answer: Some bacteria had mutations that made them resistant. They survived and reproduced, increasing the frequency of resistance in the population.
Scenario: Farmers selectively breed cows that produce more milk. They choose only the cows that produce the most milk to mate and produce offspring.
Question: How does artificial selection differ from natural selection?
Answer: Artificial selection is when humans intentionally select organisms with desirable traits, such as high milk production in cows, to reproduce. In contrast, natural selection occurs without human intervention, where organisms with traits that are beneficial for survival in their environment are more likely to reproduce.
Scenario: Scientists compare the forelimb bones of humans, cats, whales, and bats. The bones have the same basic structure but are used for different functions.
Question: What does this similarity suggest about these organisms, and why?
Answer: It suggests they share a common ancestor. The similar bone structure (homologous structures) indicates they evolved from the same ancestral species but adapted to different environments.
Question: Which kingdom consists of multicellular organisms that can carry out photosynthesis?
What is the Plantae kingdom?
Scenario: A drought causes only plants with deep roots to survive.
Question: Why doesn’t the drought “cause” plants to grow deeper roots?
Answer: The drought does not create the trait. Some plants already had deeper roots due to variation. Natural selection allows those plants to survive and reproduce.
Scenario: A population of insects lives on green leaves. A new mutation causes some insects to be yellow. Birds easily spot the yellow insects.
Question: What will likely happen to the yellow trait over time?
Answer: The yellow trait will likely decrease because those insects are more likely to be eaten before reproducing.
Question: What is the term for the process where favorable traits become more common in a population over time?
Answer: What is natural selection?
Scenario: Scientists compare the amino acid sequences of a protein in three species. Species A and B differ by 2 amino acids. Species A and C differ by 15 amino acids.
Question: Which two species are most closely related, and how do you know?
Answer: Species A and B are most closely related because fewer differences in amino acids indicate a more recent common ancestor.
Which domain consists of single-celled organisms that live in extreme environments like hot springs or salt lakes?
Answer: What is the Archaea domain?
Scenario: A student says, “Giraffes grew long necks because they needed to reach tall trees.”
Question: What is wrong with this explanation?
Answer: Traits do not develop because organisms “need” them. Some giraffes already had longer necks due to variation, and those individuals survived and reproduced more successfully.
Scenario: A small group of birds is blown to a new island with different food sources. Over many generations, their beaks become shaped differently from the original population.
Question: What evolutionary processes are likely occurring?
Answer: Natural selection and possibly speciation. Different environmental pressures favor different traits, leading to divergence.
Question: In Darwin’s theory, what kind of traits increase an organism's chance of survival and reproduction?
Answer: What are adaptations?
Scenario: Fossils of simple marine organisms are found in the lowest rock layers. Above them are fish fossils. Above those are amphibians and reptiles.
Question: What does this pattern suggest about the history of life on Earth?
Answer: It suggests that life began in oceans and gradually evolved into more complex land organisms over time.
What is the difference between Aristotle and Linneaus classification system?
Scenario: In a population of moths, most individuals are light-colored, which helps them blend in with the light-colored bark of trees. However, a small number of moths have dark-colored wings due to a genetic mutation. Over time, industrial pollution darkens the tree bark.
Question: How could this change in the environment affect the frequency of the dark-colored moths in the population?
Answer: The change in the environment would likely lead to an increase in the frequency of dark-colored moths. The dark-colored moths would blend in better with the darker tree bark, making them less visible to predators. As a result, these moths would have a better chance of surviving and reproducing, passing on the genetic mutation for dark coloration to future generations.
Scenario:
In a population of 100 beetles:
80 are green
20 are brown
Birds eat 50% of the green beetles but only 10% of the brown beetles.
Question:
After predation, how many of each color remain? Which trait is likely to increase in frequency over generations?
Answer:
Green: 80 → 40 survive
Brown: 20 → 18 survive
Brown beetles now make up a much larger proportion of survivors, so brown coloration will likely increase over generations.
Scenario: A group of finches on an isolated island has developed different beak shapes depending on the available food sources. Some have long, narrow beaks for picking insects, while others have short, thick beaks for cracking seeds.
Question: How would natural selection explain the development of these different beak shapes in the finch population over time?
Answer: Natural selection would favor finches with beak shapes that help them survive and reproduce in their environment. On the island, finches with beaks suited to the available food (long beaks for insects, short beaks for seeds) would be more likely to survive, reproduce, and pass on their traits. Over time, this would lead to a population with a variety of beak shapes adapted to the island’s food sources.
Scenario: You discover a fossil of a small, four-legged reptile in a layer of rock that is 200 million years old. Later, you find the fossil of a large, six-legged insect in a more recent layer of rock.
Question: How could these fossils help scientists understand the relationship between ancient species and modern-day species?
Answer: Fossils can show how life forms have changed over time. The reptile fossil suggests that early land-dwelling creatures evolved over millions of years into different species, eventually leading to modern reptiles. The insect fossil indicates how insect species evolved differently from reptiles and adapted to their environments in a variety of ways. By comparing these fossils, scientists can track the evolutionary lineage of different organisms.
Scenario: You are tasked with classifying a newly discovered organism. It is multicellular, has a cell wall, and uses sunlight to make its food. However, it does not have chlorophyll and does not perform photosynthesis like typical plants.
Question: How would you classify this organism, and why?
Answer: This organism could be classified as a fungus or alga, depending on its specific characteristics. If it has features similar to fungi (such as a lack of chlorophyll and a cell wall), it would likely be classified as a fungus. If it shares traits with algae, such as living in aquatic environments and having a different way of producing energy, it could be classified as an alga. The classification would depend on further examination of its genetic makeup, structure, and behavior.
Scenario: A population of birds living on an island has two types of beaks: one type is short and stout, while the other is long and thin. The short, stout beaks are effective at cracking open hard seeds, and the long, thin beaks are good for extracting nectar from flowers.
Question: What might happen to the bird population if the environment changes, and hard seeds become less common while flowers become more abundant?
Answer: Over time, natural selection would likely favor birds with long, thin beaks because they would be better able to access the abundant nectar. The birds with short, stout beaks might struggle to find enough food and could decrease in number, leading to a population shift in favor of the long-beaked birds.
Scenario: A population of rabbits is living in a cold climate where white fur helps them blend into the snowy environment. Over time, the climate warms, and the snow melts, leaving more green vegetation. Some rabbits in the population have brown fur.
Question: How might the process of natural selection change the frequency of fur color in the rabbit population over several generations?
Answer: In a warmer, less snowy environment, rabbits with brown fur would likely have a survival advantage because they blend in better with the vegetation, making them less visible to predators. Over time, natural selection would favor brown-furred rabbits, and the frequency of brown fur would increase in the population, while white-furred rabbits might become less common.