Evolution and Speciation (Part 4) Ms. Day AP Biology Chapter 24: The Origin of Life

How Does Evolution Work? Populations produce more offspring than the environment can support Carrying capacity sets the “limit” The unequal ability of individuals to survive and reproduce (i.e.-an organism’s fitness) leads to the gradual change in a population over many generations Allele frequencies (p and q) to change

RECALL: 3 Types of Natural Selection Directional Extreme form favored by natural selection Stabilizing Middle form most successful Disruptive (Diversifying) Two extreme forms successful in separate environments

Types of Evolution 1. Convergent evolution organisms that are NOT closely related independently evolve similar traits as a result of having to adapt to similar environments. Ex: Dolphins & fishes Ex: Wings of bees & bats

2. Divergent evolution 2 species gradually become different Often occurs when closely related species diversify to new habitats responsible for creation of current diversity of life on earth from the first living cells Ex: Darwin’s finches Type: Adaptive radiation

Hawaiian archipelago  Example of adaptive radiation KAUAI 5.1 million years OAHU 3.7 HAWAII 0.4 1.3 MAUI MOLOKAI LANAI Argyroxiphium sandwicense Dubautia linearis Dubautia scabra Dubautia waialealae Dubautia laxa N

3. Coevolution 2 organisms evolve (change) in response to each other Insects and the flowers (ex: orchids) they pollinate

4. Parallel Evolution 2 species evolve independently of each other, maintaining similar traits Usually occurs between unrelated species that do NOT occupy the same or similar habitats Ex: Eutherians (placental) and Marsupial mammals

Review

Two Basic Patterns of Evolutionary Change Anagenesis (phyletic evolution) transforms one species into another Cladogenesis (branching evolution) the splitting of a gene pool, giving rise to one or more new species

LE 24-2 Anagenesis Cladogenesis

How fast does evolution occur? Gradualism Species change slowly (gradually) over time Punctuated Equilibrium Species can make rapid “leaps” in evolution

Time Gradualism model Punctuated equilibrium model

What is a Species? Species is a Latin word meaning “kind” or “appearance” A population of organisms that produces viable fertile offspring in nature. They can NOT interbreed with other populations

Similarity between different species  different behaviors and songs Diversity within a species  defined by capacity to interbreed.

Speciation Speciation = the origin of new species Must explain how new species originate and how populations evolve Microevolution (genotype evolution) adaptations that evolve within a population’s gene pool Macroevolution (phenotype evolution) refers to evolutionary change at the population level Major biological changes evident in the fossil record