Evolution and Biodiversity: Origins, Niches, and Adaptations What is Evolution? Chapter 5

Key Concepts Origins of life Evolutionary processes Ecological niches Species formation Species extinction

Earth: The Just-Right, Adaptable Planet During the 3.7 billion years since life arose, the average surface temperature of the earth has remained within the range of 10-20oC. What other conditions make life on Earth possible?

Origins of Life Evidence suggests that life on earth developed in 2 phases: Chemical Evolution and Biological Evolution Chemical Evolution formation of the earth’s crust and atmosphere evolution of the biological molecules necessary for life evolution of the systems of chemical reactions needed to produce living cells (protocells) Fig. 5-2 p. 93

Animation on CD H2O CH4 Electrode CO2 N2 NH3 H2 Electrical sparks Water vapor Electrode N2 CO2 NH3 H2 Electrical sparks simulating lighting provide energy to synthesize organic compounds Condenser Cold water Cooled water containing organic compounds H2O Sample for chemical analysis Animation on CD

Modern humans (Homo sapiens) appear about 2 seconds before midnight Recorded human history begins 1/4 second before midnight Age of mammals Age of reptiles midnight Insects and amphibians invade the land Origin of life (3.6–3.8 billion years ago) Plants invade the land First fossil record of animals Plants begin invading land noon Evolution and expansion of life

How Do We Know Which Organisms Lived in the Past? Our knowledge about past life comes from fossils, chemical analysis, cores drilled out of buried ice, and DNA analysis.

Comparing Anatomy and Embryology Homologous Structures Parts that are similar in structure but different in function Humans, penguins, alligators, bats all have the same bones in their arms but they are used for different things Similar Embryos Embryos of different organisms are very similar and have similar structures early on Must have similar proteins at work Vestigial Structures Structures that are so reduced in size of function that they are merely traces of similar organs in other species (I.e. tailbone and appendix in humans) Analogous Structures Parts that are similar in function but not structure i.e. Wing of bee, bird, bat

Fossils mineralized or petrified replicas of skeletons, bones, teeth, shells, leaves, and seeds, or impressions of such items provide physical evidence of organisms Fossil record is INCOMPETE – only found and 1% of the species that are believed to have lived

Origins of Life Biological evolution change in the genetic makeup of a population of a species in successive generations, if continued long enough it can lead to the formation of a new species How do new genes get into the population: mutations, genetic drift (organisms coming in and out of the population) Populations – NOT INDIVIDUALS - evolve

Evolution and Adaptation Theory of Evolution – all species descended from earlier, ancestral species. HOMER Macroevolution - long-term, large-scale evolutionary changes through which new species are formed from ancestral species and other species are lost through extinction.

Evolution and Adaptation Microevolution - small genetic changes that occur in a population. Genes mutate, individuals are selected and populations evolve. Gene pool – set of all genes in the individuals of the population of a species Mutation – changes in the structure or number of DNA molecules in a cell Mutations are random, rare, only source of totally new alleles Exposure to mutagens Mistakes during replication

Evolution and Adaptation Natural selection Process in by which individuals of a population acquire genetically based traits that increase their chances of survival and their ability to produce offspring. Adaptation (n.) A heritable trait that enables an organism to better survive and reproduce under a given set of environmental conditions Artificial selection Humans select one or more desirable genetic traits in the population of a plant or animal.

Artificial Selection The selective breeding of domesticated plants and animals by man. Question: What’s the ancestor of the domesticated dog? Answer: WOLF This is STELLA!!!!!

Natural Selection Directional Selection (peppered moth example) Conditions necessary for natural selection: Variability – phenotypic differences in a trait Heritability – trait must have a genetic basis to evolve Differential Reproductive Success – phenotypic traits determine individual survival and success Combination of survival and reproduction is called “fitness” Survival of the Sneakiest Directional Selection (peppered moth example) Stabilizing Selection Diversifying Selection Fig. 5-4 p. 96 CD ANIMATION 4

Evolution as Genetic Change in Populations How Natural Selection Works – 3 Types Stabilizing Selection Individuals with the average form of a trait have the highest fitness Represents the optimum for most traits Results in a similar morphology between most members of the species Directional Selection Individuals that display a more extreme form of a trait have greater fitness than individuals with an average form of the trait A shift in one direction Peppered moth Disruptive DIVERSIFYING Selection Individuals with either extreme variation of a trait have greater fitness than individuals with the average form of the trait A shift in both direction, away from the center Shell color (dark rocks and light sand)

Directional Natural Selection Snail coloration best adapted to conditions Average New average Previous average Natural selection Number of individuals Number of individuals Average shifts Coloration of snails Coloration of snails Proportion of light-colored snails in population increases

Stabilizing Natural Selection Light snails eliminated Dark snails eliminated Natural selection Snails with extreme coloration are eliminated Number of individuals Number of individuals Coloration of snails Coloration of snails Average remains the same, but the number of individuals with intermediate coloration increases

Diversifying Natural Selection Intermediate-colored snails are selected against Snails with light and dark colors dominate Natural selection Light coloration is favored Dark coloration is favored Number of individuals Number of individuals Coloration of snails Coloration of snails Number of individuals with light and dark coloration increases, and the number with intermediate coloration decreases