Conditions for Natural Selection
In a forest, a single tree produces 5,000 seeds, but only 2 grow into adults. This is an example of which condition?
Overproduction of offspring
A group of lizards is washed away to a remote island during a storm and can no longer reach the mainland. What is this called?
Geographic Isolation
This "record" of life is found in rock layers, where the deepest layers usually contain the oldest, simplest organisms.
Fossil Record
This is the specific chemical code that scientists compare to see how closely related two species are.
DNA
A scientist describes a data set where the number of brown mice increased and white mice decreased after a forest fire. What is the "favorable trait"?
Brown fur/Camouflage
Within a population of rabbits, some have ears that are 4 inches long and others have ears that are 6 inches long. This is an example of which condition?
Inherited Variation
This term describes bacteria that are no longer affected by the "miracle drugs" designed to destroy them.
Antibiotic Resistance
Humans have a tailbone but no tail. This "leftover" structure is known as what?
Vestigial Structure
If a chimpanzee and a human share 98% of the same DNA, what does this suggest about their ancestry?
They share a very recent common ancestor.
You are told that a population of finches on Island A have thin beaks, and those on Island B have thick beaks. What information do you need to prove geographic isolation occurred?
Evidence of a physical barrier (the ocean) and that they were once the same species.
If a population has zero genetic variation—meaning every individual is a perfect clone—explain why natural selection would fail to happen.
There are no "favorable" traits to select; everyone would survive or die at the same rate.
A farmer notices that after 5 years of using the same weed-killer, the weeds are taller and healthier than ever. Explain why the population changed.
The resistant weeds survived and reproduced, making the trait common.
A bird’s wing and a human’s arm have different functions but the exact same bone blueprint. What are these called?
Homologous Structures
Besides DNA, scientists often compare the sequences of these "building blocks" that make up proteins.
In a lab experiment, a petri dish of bacteria is treated with penicillin. In "Generation 1," 99% die. In "Generation 10," 99% survive. Summarize what happened to the traits in this population making sure to use the term frequency in your answer.
The frequency of the resistance trait increased over time due to natural selection.
Name two abiotic factors in an ecosystem that could create a "struggle for survival" for a population of fish.
Water temperature, acidity/pH, oxygen levels, or water levels/drought.
Aside from bacteria, this group of organisms (which includes mushrooms and molds) can also evolve to resist medications.
Fungi / Antifungal Resistance
Why does the similarity of embryos (like fish and humans having Pharyngeal arches (gill slits) in the egg) provide evidence for evolution?
It shows they inherited the same developmental "blueprint" from a common ancestor.
A student claims that two species are related because they both have blue fur. Why is DNA evidence more "empirical" than just looking at fur color?
DNA shows the actual genetic heritage; fur color could be a coincidence or "convergent evolution.
Scientists find a fossil that has features of both a dinosaur and a bird. This is called a "transitional fossil." What does it illustrate?
The evolutionary path or "common ancestry" between two different groups.
Even if an organism is the strongest and fastest in its group, biology defines its "fitness" as zero if it never does this.
Reproduces/Passes on traits to offspring
Explain how geographic isolation leads to a "reduced opportunity to reproduce.
It physically prevents the two groups from meeting and exchanging DNA/mating.
Why are "analogous structures" (like a bird wing and a bee wing) NOT considered evidence of a recent common ancestor?
They have different structures/blueprints; they just evolved to do the same job.
All living things—from bacteria to humans—use the exact same genetic code. What is the reasoning for this?
All life descended from one single common ancestor that used that code.
You are given a list of three species: Species X, Y, and Z. X and Y share 90% DNA. X and Z share 70% DNA. Using reasoning, which two species shared a common ancestor most recently?
Species X and Y