Biology 20 - Chapter 4 : Mechanisms of Population Change Flashcards
Mutation
- Any change in the DNA sequence of a cell.
- Genetic variation is created through mutations, which occur continuously in the DNA of living organisms.
Selective Advantage
- A mutation that gives an organism an advantage. Any characteristic or trait that gives an organism or a genotype greater chances of surviving and reproducing than the available alternatives.
Speciation
- The formation of new species.When populations of the same species become reproductively isolated from each other and start to evolve independently.
Transformation/Divergence
- Transformation: Changes that occur within a population over time, through genetic mutations or adaptations to the environment.
Divergence: the accumulation of differences between populations that were one the same species. As populations become isolated from each other, they can experience pressures and changes causing them to diverge and become distinct species.
Natural Selection
- Nature’s way of favoring individuals with helpful traits, allowing them to survive and pass those traits to their offspring.
Selective pressure
- Nature’s way of pushing species to adapt and evolve. Factors of the environment that influence the survival and reproduction of individuals with certain traits.For example predators, competition for resources, climate changes.
Homologous and Analogous structures
- Homologous : Similarities in traits or body parts that are found in different species. Which have a common evolutionary origin. Ex forelimbs of humans, cats, bats and whales have the same basic bone structure suggesting a shared ancestry.
- Analogous : Similar traits or body parts found in different species that have a similar function but different evolutionary origins. Ex wings of a bird vs wings of insects are both for flying but evolved independently.
Adaptive Radiation
- The diversification of a common ancestral species into a variety of species, which are all differently adapted.
Gradualism
- Change occurs slowly over long periods of time. Species evolve through a continuous and gradual accumulation of small changes.
Punctuated Equilibrium
- Species experience periods of relative stability followed by rapid bursts of evolutionary change.
How mutations increase genetic variation
Genetic variation is created through mutations, which occur continuously in the DNA of living organisms. Mutations increase genetic variation by introducing changes in the DNA sequence. These changes can alter the structure and function of proteins, leading to new traits and characteristics.
Selective advantage
When a mutation gives an organism an advantage, for example it will allow an organism to better survive in its environment. Mutations that would previously have had a neutral/negative effect can sometimes be favorable when an organism’s environment is changing.
Natural Selection as a mechanism of population change
Nature’s way of picking the fittest individuals to survive and reproduce. The process where characteristics of a population of organisms change because individuals with certain inherited traits survive long enough to reproduce and pass those traits to their offspring. Some traits may be more advantageous than others, allowing individuals with those traits to better survive and reproduce. These individuals pass on their advantageous traits to their offspring, increasing the frequency of those traits in the population over time.
Evidence for evolution including the fossil record
- Fossils in young layers of rock are much more similar to today’s species than fossils found in deeper layers of rock.
- Fossils appear in chronological order in the rock layers. Ancestors are found in older rocks.
- Not all species appear in the fossil record at the same time.
Evidence for evolution including the transitional fossils
- Hundreds of transitional fossils representing intermediate forms have been discovered.
- As the fossil record improves ‘gaps’ in the fossil record are reduced.
