Section 5 Flashcards
Fixity of species
Until about 200 years ago, most scientists didn’t believe in evolution. They though all present day species of plants and animals were created in their present forms.
Evolution
A species has changed overtime. A change in the relative frequency of alleles.
Eg. Of evolution
30% of a population of bears used to carry the allele for long fur. Now 70% has this allele. Population evolved in the direction of longer fur.
Lamarck’s theory
Theory of “use and disuse”. Of an organism uses more of a certain body part, then it will tend to grow/improve during that organism’s lifetime. Underused body parts will shrink. Organism then passed this improved body part. Species evolve overtime.
Flaw in Lamarck’s theory
Only genes control traits, living things can’t change their genes. Therefore any changes in traits are purely random and beyond the control of an organism.
Theory of natural selection
Announced by Darwin and Wallace in 1858.
Organisms inherit all traits at birth, can’t change them.
Each individual in a species is unique, has its own particular combo of traits.
Some traits might give competitive advantage.
Adaptation
Any trait that increases an organisms fitness
Eg. Adaptation
Longer fur in cold climate
Niche
The role that a species plays in its environment. A species will evolve so it better fits its niche. Empty niches will be occupied by new species to evolve into.
Eg Niche
Lion is the top predator of the African grasslands
When Dino’s died, many niches were vacant. Mammals evolved and took empty niches.
Adaptive radiation
One species gives rise to a number of new ones. This way species can spread and occupy many niches.
Reproductive isolation
1 group becomes separated from the rest of its species. Evolves independently. Having a separate gene pool allows to evolve into new species.
Speciation
New species arises from an old one
Divergent evolution
Over time 2 species evolve so they become more different
Convergent évolution
2 species evolve so that they look more alike
