B 5 1 Evolution What is Evolution Evolution

B 5. 1 Evolution

What is Evolution? • Evolution- Describes all of the changes that have transformed life on Earth from the beginning of life until today • Evolution is the unifying theme of Biology • Evolution can occur: – On a small scale • Called microevolution which effects a single population – Or a large scale • Called macroevolution which effects across several populations

Natural Selection • Natural selection- individuals in a population have different traits which allow them to interact with the environment better or worse than the rest of the population. • This means changes in the inherited traits overtime. • Most of the time, these changes increase the species’ fitness in the environment. – Fitness meaning ability to live and reproduce • There are 4 main principles to natural selection.

4 Principles of Natural Selection • Overproduction of Offspring – Ability of a population to have many offspring raises the chance that some will survive, but also raises competition for resources. • Ex. Nemo • Variation – varying of inherited traits of the individuals – only exists in phenotype of members of population – The phenotype may change the organism’s ability to find, obtain, or use resources (food, H 2 O, shelter etc. ) or effect the ability to reproduce. – Controlled by individual’s genotype and environment. • If the phenotypes do not interact well with the environment the organism will either die or produce fewer offspring than those that can interact well.

4 Principles of Natural Selection • Adaptation – Makes organisms better able to survive and reproduce • With every generation the certain inherited traits that were due to variation will be expressed more of the population. • Also with every generation the offspring that have a harder time meet day to day needs become fewer in the population – Organisms that have a harder time surviving will more likely to die first, reproduce less and have fewer “fit” offspring. – This is how the gene pool changes over time. • “Fitness” is used to measure how much a particular trait helps something reproduce in an environment and results from adaptations. • Sometimes known as “Survival of the Fittest”.

4 Principles of Natural Selection • Decent with modification – As environment changes, natural selection can make new populations, phenotypes, and adapt to new conditions. – Natural selection can produce completely new populations with different roles in the ecosystem than their ancestors. The next generation will have the new roles and genes from the previous one. – More individuals will have successful traits that are beneficial to the environment because the others have been killed off.