Topic 5: Evolution Flashcards
Evolution
Change over time; change in the frequency (how often they appear) of selected genes within a population of organisms
Organisms tend to become more BLANK as they evolve through time
complex
What types of genes will increase in number as time goes on?
Genes with high adaptive value: these allow an organism to survive. They will pass from one generation to another
Evolution happens faster if…
The environment is changing
Evolution occurs as a result of…
Natural selection
Who proposed the theory of natural selection in 1859?
Charles Darwin
Natural Selection
If an organism has genes with adaptive value, they reproduce, passing the genes to the next generation. This causes the gene to become more common in the population. In a changing environment, favorable genes accumulate rapidly changing the appearance or behaviors of the populations
What may happen if a species doesn’t adapt/evolve in a changing environment?
They may go extinct
4 steps of natural selection
- Overproduction
- Competition
- Variation
- Selection and Reproduction
Overproduction
too many offspring are created. They can’t all survive because of limited resources in the environment.
Competition
Because species share common niches they will compete for food, space, mates, etc.
Variation
Sexual reproduction creates new combinations of genes
Mutations
change the DNA/gene slightly
Why are individuals of a population different?
They contain different genetic information because of sexual reproduction and mutations
Selection & Reproduction
The genes that are not adapted to the environment are selected against (die).
Genes that have adaptive value will…
Survive and be passed on to offspring.
If a population lacks genetic variation (due to asexual reproduction, no mutations, inbreeding, etc.) they will…
Not be able to evolve to a changing environment
If two species share a common ancestry…
They are related. They will have similar DNA, proteins, embryonic development, bone structures.
Evolutionary tree (phylogenic tree)
Diagram that illustrates the change of species over time.
The very bottom of the evolutionary tree is…
The common ancestor
Lines that end before the top of the evolutionary tree represent…
Species that are now extinct.
Lines that reach the top of the evolutionary tree are…
Currently living species
Branches on the evolutionary tree that are drawn close to one another are BLANK than branches drawn farther apart
More closely related
Fossil Record
a collection of fossils documenting the history of life on Earth. These fossils can teach us about an extinct organism’s size, shape, and/or behavior.
Geologic Time
