biology exam Flashcards
Homologous Structures:
similar physical features in organisms that share a common ancestor, but the features serve completely different functions.
Analogous Structures:
Body parts that look alike and serve the same purpose, but are found in animals that aren’t closely related
Vestigial Structures:
These are body parts that don’t have a clear function anymore, likely leftovers from our evolutionary past.
Darwin’s Observations and evidence for natural selection:
Darwin noticed that organisms vary, and those with traits better suited for their environment are more likely to survive and pass on their traits to the next generation.
Darwin’s Observations and evidence for natural selection:overproduction
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Overproduction, in the context of evolution, refers to the tendency of species to produce more offspring than the environment can support. This leads to competition for limited resources, a key concept in Darwin’s theory of natural selection.
Darwin’s Observations and evidence for natural selection:variation
Variation - there are variations between members of the same species
Darwin’s Observations and evidence for natural selection:adaptation
Adaptation refers to the process by which organisms evolve features or behaviors that enhance their survival and reproduction in a specific environment.And will be passed on
Main Sources of Evidence for Evolution:
Fossils (ancient remains), comparing body structures, studying genes, looking at embryos(Embryos are early stages in the development of multicellular organisms, occurring after fertilization of an egg (ovum) by sperm.), and analyzing where species are found.
Selection Patterns:
Imagine a population of animals. If average traits are favored, that’s stabilizing selection. If extreme traits are favored, that’s disruptive selection. If one extreme trait is favored, that’s directional selection.
Stabilizing Selection:
Meaning: In stabilizing selection, the average or intermediate traits in a population are favored, while extreme traits at both ends of the spectrum are selected against.
Outcome: Over time, this leads to a reduction in the overall variation of traits within the population, and the traits tend to stabilize around the average.
Example: Imagine a population of bird beak sizes. If birds with both very short and very long beaks struggle to survive because they can’t efficiently feed on available food sources, birds with medium-sized beaks might have an advantage. Stabilizing selection would favor the medium-sized beaks, reducing the frequency of extremely short or long beaks in the population.
Disruptive Selection:
Meaning: In disruptive selection, extreme traits at both ends of the spectrum are favored, while individuals with average traits may be at a disadvantage.
Outcome: This can lead to the splitting of a population into two or more distinct groups, each with its own set of extreme traits.
Example: Consider a population of rabbits with fur color. If the environment contains both dark and light areas, rabbits with extremely dark fur may be better camouflaged in dark areas, while rabbits with extremely light fur may be better camouflaged in light areas. Disruptive selection could lead to two subpopulations with distinct fur colors.
Directional Selection:
Meaning: In directional selection, one extreme trait is favored over the other extreme or the average trait. The population shifts toward the favored extreme.
Outcome: Over time, the frequency of the favored trait increases, while the frequency of the less favored trait decreases.
Example: Imagine a population of giraffes with neck length. If the environment changes, and taller trees become the primary food source, giraffes with longer necks may have a feeding advantage. Directional selection would favor the increase in the frequency of giraffes with longer necks in the population.
