Natural Selection Pre-AP Biology

Addie’s Case – Patterns Addie was cut while playing on the playground in 2011. She went to the hospital after becoming sick due to an infection caused by one type of bacteria from this cut. Doctors gave her an antibiotic that worked for a while, but then stopped working. She ended up getting another infection from a different type of bacteria while in the hospital. Doctors then gave her a different antibiotic that worked for a while, but then it stopped being effective and Addie got sicker. They tried a third antibiotic and Addie started to improve, but this antibiotic also stopped being effective and she got worse once again. They repeated this process trying every antibiotic available to them.

Addie’s Case - Types of Bacteria Two different species – Staphylococcus and Stenotrophomonas Some of both kinds of bacteria appear to have been killed by antibiotics. On the other hand, some of both kinds of bacteria were not killed by those antibiotics. It appears that there are two types of bacteria within each species —those that are resistant to an antibiotic (and lived) and those that are not resistant to an antibiotic (and died).

Addie’s Case - Antibiotic Cycles New Antibiotic Got better Got Worse Pan-Resistant Bacteria

Learning Goals 1. Define "Evolution" & "Natural Selection". 2. Describe the 4 steps of Natural Selection, giving an example of each. 3. Explain the importance of "Variation". 4. Does Natural Selection act on an organism phenotype or genotoype? Explain! 5. List the 5 evidences that support the Theory of Evolution.

Theory of Evolution Evolution: The process of change over time Specifically, a change in the frequency of a gene or allele in a population over time

Charles Darwin Father of Evolution Proposed a mechanism for evolution, natural selection Darwin went on a 5-year trip around the world on the ship, the HMS Beagle As the ship’s naturalist, he made observations of organisms in South America and the Galapagos Islands Wrote a book, “Origin of the Species”

Darwin’s Finches The shape of the beak is adapted to the diet and environment of the finch. Each finch ate a different diet so they occupied a different niche and created less competition.

Natural Selection Natural Selection: Organisms that are best adapted to an environment survive and reproduce more than others Adaptation: an inherited trait that increases an organism’s chances of survival Behavior, Physical, or Physiological traits Darwin’s Theory of Natural Selection occurs in four steps: Overproduction Variation Competition Selection

What adaptations do you see?

1. Overproduction Each species produces more offspring that can survive

2. Variation Each individual has a unique combination of inherited traits from their parents.

Why is Variation Important? Because the environment changes. The more variation within a species, the more likely it will survive EX: If everyone is the same, they are all vulnerable to the same environmental changes or diseases The more variation of types of species in an habitat, the more likely at least some will survive EX: Dinosaurs replaced by mammals

Which community has a better chance of surviving a natural disaster? Community A Community B

3. Competition Fitness: the ability to survive and reproduce Individuals COMPETE for limited resources: Food, water, space, mates Natural selection occurs through “Survival of the fittest” Fitness: the ability to survive and reproduce Not all individuals survive to adulthood

4. Selection The individuals with the best traits / adaptations will survive and have the opportunity to pass on it’s traits to offspring. Natural selection acts on the phenotype (physical appearance), not the genotype (genetic makeup) Ex: When a predator finds its prey, it is due to the prey’s physical characteristics, like color or slow speed, not the alleles (BB, Bb)

Individuals with traits that are not well suited to their environment either die or leave few offspring. Evolution occurs when good traits build up in a population over many generations and bad traits are eliminated by the death of the individuals.

Peppered Moth A Which moth will the bird catch? B

Descent with Modification Descent with Modification – each living species has descended, with changes, from other species over time. Common Descent – all living organisms are related to one another

Cladogram: Shows evolutionary relationships and common ancestry.

Evidence for Evolution: Fossil Record Homologous Body Structures Vestigial Organs Embryology Biochemical Evidence

The Fossil Record Fossils: a record of the history of life on Earth

Archaeopteryx Missing link between reptiles and birds

Pangea

Homologous Body Structures Homologous Body Structures: similar anatomy in different types of animals because of common ancestor

Vestigial Structures Vestigial Structures: “leftover” traces of evolution that serve no purpose or function

Embryology Embryology: embryos of all vertebrates are very similar early on

Biochemical Evidence Biochemistry: DNA with more similar sequences suggest species are more closely related EX: Humans and chimpanzees share more than 98% of identical DNA sequences

Speciation is the formation of new species Speciation is the formation of new species. A species is a group of organisms that breed with one another and produce fertile offspring.

Isolating Mechanisms As new species evolve, populations become reproductively isolated from each other. When the members of two populations cannot interbreed and produce fertile offspring, reproductive isolation has occurred. (3 types)

Behavioral Isolation  Behavioral isolation occurs when two populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior.

Geographic Isolation  Geographic isolation occurs when two populations are separated by geographic barriers such as rivers or mountains.

Copyright Pearson Prentice Hall

Temporal Isolation Temporal isolation occurs when two or more species reproduce at different times.

Coral Snake (Venomous) Milk Snake (Not Venomous)

Stick Mantid

Flower Mantid