Natural Selection EQ: How can a change in the environment initiate change in a population?

Heritability The ability of a trait to be passed down from one generation to the next Some variation is due to Heredity (inherited)

Evolution Evolution: the process of biological change by which descendants come to differ from their ancestors

Charles Darwin Naturalist who founded the ideal that biological traits become either more or less common in a population as a result of inheritance on the reproductive success of organisms interacting with their environment. Studied animals on the Galapagos islands, off the coast of South America, and determined that they evolved differently based on their environment He stated that

Main Idea I Darwin observed variation among island species

Darwin’s Examples include : Saddle-backed Tortoises Domed tortoises Have long necks and legs because they feed off trees Have shorter necks and legs because they feed of grass

Darwin observed that species could adapt to their environment Main idea ii Darwin observed that species could adapt to their environment

An adaptation: Examples: Finches with strong, thick beaks live in areas with a lot of large, hard-shelled nuts 2. finches with more delicate beaks are found where insects or fruits are widely available.

Main idea Iii Darwin observed fossils showing evidence that organisms have changed over time .

Fossil evidence included Glyptodon, a giant extinct armadillo that resembled living armadillos

Natural Selection Natural selection is a mechanism of evolution by which individuals that have the best traits for the current environment survive and reproduce passing on their genes to the next generation. natural selection is a process by which individuals with inherited characteristics well-suited to the environment leave more offspring on average than do other individuals – hence passing on those characteristics

Natural Selection: conditions Variation: difference in physical traits of individuals in the group it belongs Caused by: Mutations (changes in DNA) Sexual reproduction Mixing of alleles (crossing over) Random mate selection

Result Variation leads to adaptation Adaptation: A certain variation that allows an individual to survive better than others in the same environment Which mouse is better adapted for the environment?

Condition for Natural Selection: Variation Adaptation examples: Finches with strong, thick beaks live in areas with a lot of large, hard- shelled nuts Finches with more delicate beaks are found where insects or fruits are widely available.

When the environment changes When faced with a change in environmental condition, a population of a species can get MAD: MIGRATE or Move Adapt DIE

Natural Selection: conditions Overpopulation: when organisms produce more offspring than can survive increase competition for resources Causes a struggle for survival

Struggle for Survival Populations would grow if resources were unlimited. Population- all of the individuals of a species living in a given area Recall: what are the limiting factors that keep a population small? There is competition for the limited resources Disease and a limited food supply keep the population smaller.

Natural Selection = Survival of the fittest?? Why is natural selection sometimes referred to as “Survival of the fittest?” What is Fitness? Fitness is a measure of the ability to survive & produce more offspring (have more babies!) Natural selection acts on the PHENOTYPE Survival of the fittest (genes= traits)

Survival of the fittest Organisms that are the best ‘fit’(adapted) for the environment will survive and reproduce thus passing on those genes (traits)

Natural Selection: conditions Differential Reproductive Success: organisms that are best adapted for their environment survive and reproduce, thus passing on the preferred trait More individuals will have the trait in every following generation due to reproduction

Natural Selection Organisms that are best adapted to the environment will survive The successful traits will spread through the population due to reproduction This change in the frequency of alleles in the population is evolution. Fitness is a measure of the ability to survive & produce more offspring Survival of the fittest (genes) Natural selection acts on the PHENOTYPE (NS can only act on traits that exist) Green bugs die and as they get eaten they are less likely to reproduce. Therefore, the orange bugs reproduce more and the orange allele becomes more frequent than the green allele. The orange bugs reproduce more passing on the orange allele as the green bugs get eaten they reproduce less and the green allele dies off.

Natural Selection Artificial Selection Artificial Selection- humans select the traits they wanted. Natural Selection- environment (nature) chooses who will survive

Check for Understanding – QKA In the 1940s, the scientist J. B. S. Haldane linked many human red blood cell disorders with the tropical regions where malaria occurs. Haldane hypothesized that the widespread presence of these red blood cell disorders as well as traits that protect individuals from malaria were the result of natural selection. Haldane’s hypothesis was later confirmed by the research of A. C. Allison. The resistance to malaria carried by individuals in areas where malaria is widespread is the result of — a vaccine against malaria the individuals’ genetic composition antibiotic medications the individuals’ behavior in avoiding those with the infection

Survival of the fittest Lab C- level 2 voice H- ask three before me A- complete the analysis questions from the three trials M- remain seated at your table, walking around will be a strike P- complete the data table and discussion questions Success