Chapter 15 Evolution and Diversity

Standard 3.1 Different species might look dissimilar, but the unity among organisms becomes apparent from an analysis of internal structures, the similarity of their chemical processes, and the evidence of common ancestry (e.g., homologous and analogous structures, embryology, fossil record, genetic data).

Evidence of common ancestry Homologous structures Embryology Genetic data

Homologous structures Structural features with a common evolutionary origin Analogous structures Structures that do not have a common evolutionary origin but are similar in function

Organisms from different species have similar developmental patterns

hollow nerve cord tail notochord pharyngeal slits The phylum Chordata contains all vertebrates and some invertebrates. Chordates share four features at some stage of development. – notochord – hollow nerve cord – pharyngeal slits – tail

hollow nerve cord tail notochord pharyngeal slits Most chordates lose some or all of these characteristics in adulthood.

How and why do new species form?

Evolution Def: a change in a population’s genetic makeup that takes place over many generations. The process or mechanism that results in evolution is called Natural Selection

Lamark vs Darwin

Bell Work

From yesterday

Lamark vs Darwin

Species and populations Species: a group of organisms that can breed and produce fertile offspring Population: a group of individuals of the same species that can interbreed.

Speciation The process by which one species gives rise to another. An example of geographic isolation

Standard Characteristics of populations change through the mechanism of natural selection. These biological adaptations, including changes in structures, behaviors, and/or physiology, may enhance or limit survival and reproductive success within a particular environment.

Adaptations An inherited characteristic that increases an organism’s chances of surviving in a particular environment. Fitness: survival + reproduction – An organism’s ability to survive and reproduce in an environment is its fitness. Situation: an environment has hot summers and cold, snowy winters. Describe one adaptations that would make a mammal fit for this environment.

Types of adaptations 1. Structural – form that the organism takes – Arctic fox has small ears, fennec fox has large ears 2. Behavioral – innate (inherited) actions that individuals of the species perform. – Arctic fox can be active at any time of day – Fennec fox is nocturnal.

Types of adaptations 3.Physiological– adaptations related to biochemical processes within the organism’s body. – Arctic fox more effective at storing food energy as fat. Breeding season June-Aug. – Fennec fox effective at getting moisture needs met from fruit, roots and leaves. Breeding season in Jan/Feb

Structural Adaptations Mimicry Structural adaptation that enables one species to resemble another. Why? Camouflage Structural adaptation enabling a species to blend with its surroundings.

Practice

Bell Work EOI question

Homologous structures Structural features with a common evolutionary origin Analogous structures Structures that do not have a common evolutionary origin but are similar in function

Patterns in evolution: limb bones

Patterns in evolution: Powered flight Birds use feathers attached to arm, bats have a membrane stretched between digits

Patterns in Evolution: Convergence New world cactusAfrican euphorb South Am.Australia the development of a similar anatomical feature in distinct species lines after divergence from a common ancestor that did not have the initial trait that led to it.

Patterns in Evolution: Divergence Same lineage, evolving apart to be more different. Leads to speciation

HMS Beagle visits the Galapagos video – arrival Video-finches video –Video

Variation is important

Sources of Variation 1.Meiosis – Each sex cell has a different combination of alleles. – Cross-overs

Sources of Variation 2. Mutation – Harmful – Neutral – Beneficial

Mutations create variation Deleterious Advantageous Neutral

Natural selection acts on variations

Practice

Populations evolve, not individuals Gene pool- all the alleles of a population’s genes. Allelic frequency – percentage of any specific allele in the gene pool p + q = 1 A=? a = ? p =.5 q =.5 37% of brown rabbits die, 100% white a= 6 q = 6/20 =.3 A=14 P = ? 3 rd generation p (A) =.85 q (a) =.15

Populations in Genetic equilibrium are not evolving. Genetic equilibrium – population in which the frequency of alleles remains the same over generations. 3 rd generation p (A) =.85 q (a) =.15 4 th generation p (A) =.85 q (a) =.15 5 th generation p (A) =.85 q (a) =.15

Allele frequency

Eagle population crashes. Now what?

What causes changes to genetic equilibrium? A factor that can change the allele frequencies – Mutation – i.e new color of rabbit – Genetic drift – the alteration of allelic frequencies by chance events.

What causes changes to genetic equilibrium? A factor that can change the allele frequencies – Gene flow – transport of genes by migrating individuals.

Extra

the large plant family Leguminosae (or Fabaceae), typified by herbaceous plants, shrubs, trees, and vines having usually compound leaves, clusters of irregular, keeled flowers, and fruit in the form of a pod splitting along both sides, and including beans, peas, acacia, alfalfa, clover, indigo, lentil, mesquite, mimosa, and peanut.