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

Practice Problem #1 Red color (R) is dominant to yellow color (r) in flowers. In a population of 241 turtles, 34 are yellow. What are the allele frequencies? What percentage of each genotype are in this population?

ANSWER KEY R= Red r = yellow 34/241= 0.14 = white = rr= q 2 √0.14=√q 2 q = 0.37 then p = 0.63 RR = p 2 = (0.63) 2 = = 39.69% Rr = 2pq = 2(0.63)(0.37) = = 46.62% rr = q 2 = (0.37) 2 = = 13.69%

Practice Problem #2 Red color (R) is dominant to yellow color (r) in flowers. In a population of 241 turtles, 14 are rr, 200 are Rr and 27 are RR. What are the allele frequencies? What percentage of each genotype are in this population?

ANSWER KEY R= Red r = yellow gene pool= 482 alleles (241 flowers x 2) R = p = = 254 AA Aa  p = 254/482 or 0.53 r = q = = 228 aa Aa  q = 228/482 or 0.47 RR = p 2 = (0.53) 2 = = 28.09% Rr = 2pq = 2(0.53)(0.47) = = 49.82% rr = q 2 = (0.47) 2 = = 22.09%

What is Natural Selection? The process by which individuals leave more offspring on average than do other individuals in the same population. HOW? An organism’s environment (habitat) favors certain adaptations (characteristics or behaviors) that allows the organism to better survive and reproduce

Types of Adaptations Protective Coloring –Camouflage and Mimicry Physiological Adaptations –Reproductive/Hormonal Changes –Color changes Behavioral Adaptations –Courtship dances/ songs –“Fighting” tactics Also arise in response to environmental pressures –Temperature, Antibiotic/pesticide resistance

RECALL: Evidence for Evolution Fossil record Comparative Anatomy –Homologous structures –Analogous structures Comparative Embryology Vestigial structures Molecular biology (DNA/RNA/protein amino acid differences) Biogeography Field studies

REVIEW: What is a Population? Populations evolve over MANY generations, individuals do NOT evolve Populations are groups of interbreeding individuals that live in the same place at the same time Individuals in a population compete for resources with each other

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

Mechanism for change in a population of organisms Animals who have greater fitness survive in environment and live to reproduce Random changes in DNA (mutations) can lead to greater or less fitness –Produced by Sexual Reproduction –Allow for DIVERSITY in a Population Adaptations allow an organism to survive better in their environment

RECALL: 3 Types of Natural Selection Directional –Extreme form favored by natural selection Stabilizing –Middle form most successful Disruptive –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 the creation of the current diversity of life on earth from the first living cells Ex: Darwin’s finches Type: Adaptive radiation

Adaptive Radiation Example of divergent evolution Adapted species from a common ancestor when they are introduced to new environmental opportunities Typically occurs when a few organisms make their way to new, usually distant areas OR mass extinctions occur, which open up new niches

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

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

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 Two Basic Patterns of Evolutionary Change

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 = 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 Speciation