Just how do species change over time???? Early atmosphere, evidence, natural selection and disease agents influence natural selection.

● Evolution “ simple” definition: change over time ● Evolution helps us to understand the history of life.

 The central idea of biological evolution is that all life on Earth shares a common ancestor, just as you and your cousins share a common grandmother

● Atmosphere contained all of the following gases: o Nitrogen o Ammonia o Methane o Carbon Dioxide o Water o Hydrogen ● No oxygen….oxygen came later with photosynthesis.

 Experiment conducted by Miller and Urey proposed simple- organic molecules could have been synthesized in the atmosphere of early Earth and rained down into the oceans.

 Adaptations  Fossil Record  Comparative Anatomy  Embryological Development  DNA Similarities

 All organisms have adaptations which help them survive in their particular environment  Adaptation: a structure or behavior that helps an organism better survive in its environment  Examples: Mimicry, camouflage and physiological

 Mimicry: a structural adaptation that enables one species to resemble another species ◦ E.g. A harmless species might mimic a poisonous one

 Camouflage: a structural adaptation that allows a species to blend in with its surroundings

 Many bacteria have evolved resistance to antibiotics in the last 50 years  Pests have evolved resistance to pesticides

 Fossil: Any trace of a dead organism ◦ Fossils show the evolution of species over the past millions of years ◦ Fossil evidence proves that modern species have evolved from ancient species

Puijila the walking seal

Tiktaalik

Archaeopteryx

 Homologous structures: Body structures on different organisms that are similar in structure (same bones) and evolved from a common ancestor

Homologous Structures

 Analogous structures: Body structures on different organisms that are similar in function but did not evolve from the same ancestor (bird wing and butterfly wing)

Analogous Wing Structures Moth (insect) Pterodactyl (reptile) Bird Bat (mammal)

 Vestigial structure: body structure in an organism that no longer serves its original purpose but was useful to an ancestor (useless wings on the African ostrich)

 Early in development, human embryos and embryos of all other vertebrates are very similar, which suggests that all vertebrates are related

 Nearly all organisms have DNA, ATP, and many of the same proteins and enzymes  The DNA (genes) of closely related organisms looks very similar

 Mutations  Genetic Drift  Gene Flow  Natural Selection

 Gene pool: collectively, all of the alleles of the population’s genes  Allelic frequency: the percentage of any specific allele in the gene pool  Genes can enter and leave a population’s gene pool for many reasons  Populations in which the gene pool is not changing are said to be in genetic equilibrium

 New genes can be added to the population by errors in DNA copying called mutations  Most mutations are neutral or bad!

 Very very rarely a mutation might come along that improves an organism’s chance at survival or reproduction  These mutant genes will be passed along to offspring and become more common in the gene pool over time  If the mutation offers a large advantage, eventually (after many generations) all members of the population will have the beneficial mutation

◦ Artificial Selection: Humans choose individuals with certain traits for breeding ◦ After many generations of selection, dramatic evolutionary changes can result  Dogs  Fruits/Vegetables  Livestock

 Gene flow: the transport of genes by traveling individuals ◦ When an individual leaves a population, its genes are lost from the gene pool ◦ When an individual enters a population, its genes are added to the gene pool

 Genetic drift: when allelic frequencies are changed by random events in a isolated population ◦ Example: diseases, natural disasters, mating habits

 There are 3 basic types of natural selection ◦ Directional Selection ◦ Stabilizing Selection ◦ Disruptive Selection

 Directional selection: favors one of the extreme variations of a trait ◦ E.g. Male peacock tail feathers: Females favor larger tail feathers. Therefore males with larger feathers reproduced more often. Over many generations tail feathers grow larger and larger

 Stabilizing selection: favors average individuals in a population ◦ E.g. Human infants: Too small = bad; too large = bad; average = good

 Disruptive selection: favors individuals with either extreme of a trait but intermediate individuals have a disadvantage ◦ E.g. Cuddlefish (a type of squid): Being large is an advantage because females prefer larger males. Being small is an advantage also. Small males impersonate females trick the females into mating.

 A certain population may become isolated and evolve to fit new or different environmental conditions  The isolated population may change so much that it can no longer mate with the original population ◦ Similar to the evolution of new languages

 There are several reasons why similar populations no longer breed, creating new species: ◦ Geographic Isolation ◦ Reproductive Isolation

North rim of Grand Canyon South rim of Grand Canyon

 Gradualism: idea that species originate through a gradual change of adaptations (longer than 10,000 years) ◦ E.g. Fossil evidence shows that sea lilies evolved slowly and steadily over time  Punctuated equilibrium: idea that species originate in rapid bursts (10,000 years or less) with long periods of genetic equilibrium in between ◦ Global ice age causes rapid adaptation of thick fur  Both gradualism and punctuated equilibrium are known to occur

 Divergent evolution: species that once were similar become increasingly different ◦ Happens when populations adapt to different environments

 Convergent evolution: distantly related organisms evolve to become more similar ◦ Happens when unrelated species adapt to similar environments, possibly in different parts of the world

 English naturalist who proposed the theory of evolution by natural selection

 Darwin sailed around the world on the HMS Beagle and carefully studied thousands of different plants and animals

 On the Galapagos Islands Darwin found very strange plants and animals that don’t exist anywhere else in the world!

 Different islands have different types of finches not found on any other islands.

 Evolution is the gradual change in a population over time  Darwin was the first scientist to realize that evolution can work by natural selection. ◦ Natural Selection – Organisms with traits well suited to an environment are more likely to survive and produce more offspring than organisms without these favorable traits  “Survival of the fittest”  E.g. Thicker fur is a favorable trait in cold environments

 Evolution by natural selection happens in populations, not individuals. A single organism cannot evolve. Populations evolve.  Populations evolve because there is variation  Variation causes some organisms to be better fit than others. These better fit organisms are more likely to survive and pass their genes to the next generation

 Organisms with stronger immune systems are more likely to survive pathogens.  Eventually, the species that builds up antibodies for this particular pathogen will thrive.

 The bacteria that build up a resistance the antibiotics survive.  The ones that do not also die, just like in animals and plants.

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