5.4 Evolution

5.4.1 Define evolution cumulative change in the heritable characteristics of a population. ‘heritable’ – changes must be passed on genetically from one generation to the next implies that evolution doesn’t happen overnight ‘cumulative’ - one change isn’t enough to have major impact on the species ‘population’ - changes do not affect just one individual

5.4.2 Outline evidence for evolution. Fossil record transition species Comparative Anatomy homologous & vestigial structures Comparative Embryology embryonic development Molecular record protein & DNA sequence Artificial selection human-caused evolution

Fossil record Layers of sedimentary rock contain fossils new layers cover older ones, creating a record over time fossils within layers show that a succession of organisms have populated Earth throughout a long period of time

Fossil record A record showing us that today’s organisms descended from ancestral species Millions of years ago 50 100 150 200 250 300 350 400 450 500 550 60 55 45 40 35 30 25 20 15 10 5 Equus Hyracotherium Mesohippus Merychippus Nannippus Body size (kg)

Fossil record A record showing us that today’s organisms descended from ancestral species

Comparative Anatomy Homologous structures Similar structure Similar development Different functions Evidence of close evolutionary relationship recent common ancestor

Comparative Anatomy Homologous structures similarities in characteristics resulting from common ancestry Results of adaptive radiation - emergence of many species from common ancestor All vertebrates have similar bone structures in their limbs

Comparative Anatomy Separate evolution of structures Analogous structures Separate evolution of structures similar functions similar external form different internal structure & development different origin no evolutionary relationship Don’t be fooled by their looks!

Comparative Anatomy Analogous structures Flight evolved in 3 separate animal groups evolved similar “solution” to similar “problems” may have developed as a result of convergent evolution – unrelated species share the same environment (similar environmental pressures) and independently evolve similar structures

Comparative Anatomy Analogous structures Fish: aquatic vertebrates Dolphins: aquatic mammals similar adaptations to life in the sea not closely related Those fins & tails & sleek bodies are analogous structures!

Comparative Anatomy Homologous structures Analogous structures Results from: Adaptive radiation Common ancestor Similar origin Different functions Ex. wing of bat, human arm, dolphin flipper Results from: Convergent evolution Different ancestors Different origin Similar functions Ex. wings of bird, wings of insect Remember: Convergent evolution Adaptive radiation

Comparative Anatomy Vestigial structures Modern animals may have structures that serve little or no function remnants of structures that were functional in ancestral species deleterious mutations accumulate in genes for non-critical structures without reducing fitness snakes & whales — remains of pelvis & leg bones of walking ancestors eyes on blind cave fish human tail bone, appendix

Comparative Anatomy Vestigial structures PBS: Whales in the Making http://www.pbs.org/wgbh/evolution/library/03/4/quicktime/l_034_05.html

Comparative embryology Similar embryological development in closely related species all vertebrate embryos have similar structures at different stages of development gill pouch in fish, frog, snake, birds, human, etc.

Molecular record DNA & proteins are a molecular record of evolutionary relationships Closely related species have sequences that are more similar than distantly related species 25 50 75 100 125 Millions of years ago Horse/ donkey Sheep/ goat Goat/cow Llama/ cow Pig/ Rabbit/ rodent Horse/cow Human/rodent Dog/ Human/ Human/kangaroo Nucleotide substitutions

Molecular record Human Macaque Dog Bird Frog Lamprey 32 45 67 125 20 30 40 50 60 70 80 90 100 110 120 Number of amino acid differences between hemoglobin (146 aa) of vertebrate species and that of humans

Artificial selection (selective breeding) Artificial breeding can use variations in populations to create vastly different “breeds” & “varieties” line of evidence that supports evolution by natural selection the breeding of domestic plants and animals to produce specific desirable traits (ex. different breeds of dogs) people are doing the “selecting” rather than the environment

5.4.3 State that populations tend to produce more offspring than the environment can support. Natural populations (a population consists of all the individuals of one species in a particular area) of all organisms have the potential to increase rapidly – organisms produce far more offspring than can possibly survive

5.4.3 State that populations tend to produce more offspring than the environment can support. More than needed to keep species around More than K (carrying capacity) can support, but limited resources Intraspecific competition Some have competitive advantage such as traits, behaviors, symbiosis) More fit (competing for resources, fighting disease, etc.) = More likely to successfully reproduce Freq of these alleles higher in next generation

5.4.4 Explain that the consequence of the potential overproduction of offspring is a struggle for survival.

Some individuals selected FOR 5.4.4 Explain that the consequence of the potential overproduction of offspring is a struggle for survival. Some individuals selected FOR Some selected AGAINST Survivors (selected FOR) form new breeding population Increases freq of advantageous alleles

5.4.5 State that the members of a species show variation. Individual members of a population differ from one another in their ability to obtain resources, withstand environmental extremes, escape predators etc. (Variation)

5.4.5 State that the members of a species show variation. At least some of the variation among individuals in traits that affect survival and reproduction is due to genetic differences that can be passed on from parent to offspring – natural selection Over many generations, differential, or unequal, reproduction among individuals with different genetic makeup changes the overall genetic composition of the population – evolution Evolution is the result of natural selection

5.4.6 Explain how sexual reproduction promotes variation in a species.

5.4.6 Explain how sexual reproduction promotes variation in a species. MIXING IT UP w/MEIOSIS! Random assortment of chromosomes in Metaphase I 2^n combinations of chroms in daughter cells 8,388,608 in humans!! Crossing-over in Prophase I New combos of alleles on a chromosomes Random fertilization  any gamete can fertilize any gamete from the other individual

5.4.7 Explain how natural selection leads to evolution.

Darwin’s Theory of Natural Selection: Populations produce more offspring than can possibly survive. (overproduction) Individuals in a population vary extensively from each other, mostly due to inheritance. (variation) Struggle to survive: individuals whose inherited characteristics best fit to environment leave more offspring than less fit. (survival of the fittest) Unequal ability of individuals to survive and reproduce leads to gradual change in population. (adaptation) Favorable characteristics accumulate over generations – (descent with modification).

5.4.7 Explain how natural selection leads to evolution. Individuals with genetic characteristics that are WELL-adapted for environment Tend to be MORE successful at accessing resources And thus have BETTER chance of surviving to maturity Since they survive to adulthood, these successful organisms have a better chance to reproduce and pass on their genetic characteristics to the next generation. Over many generations, accumulation of changes in the heritable characteristics of a population results in evolution. THE GENE POOL HAS CHANGED!

5.4.8 Explain 2 examples of evolution in response to environmental change. (one must be antibiotic resistance in bacteria)

5.4.8 Explain 2 examples of evolution in response to environmental change. (one must be antibiotic resistance in bacteria) http://www.sumanasinc.com/scienceinfocus/sif_antibiotics.html

5.4.8 Explain 2 examples of evolution in response to environmental change – peppered moth melanism

5.4.8 Explain 2 examples of evolution in response to environmental change – peppered moth melanism

5.4.8 Explain 2 examples of evolution in response to environmental change – insecticide resistance – evolution in action Insecticide & drug resistance insecticide didn’t kill all individuals resistant survivors reproduce resistance is inherited insecticide becomes less & less effective