EVOLUTION

WHAT IS EVOLUTION? To evolve: to change A theory stating that all life has changed from simpler life to more complex life Occurs over LONG periods of time Evolution often supports that organisms have evolved from a common ancestor

The theory of evolution The most common theory accepted by scientists today was tested in 1953 by Stanley Miller and Harold Urey. Their apparatus simulated conditions on early Earth. It showed that chemical reactions created amino acids (organic compounds represented life).

The theory of evolution Jean-Baptist Lamark was a French naturalist who recognized that things change over time. His explanations were: Tendency towards perfection Use and disuse= if you use it, you keep it; if you don’t, you lose it Inheritance of acquired traits= traits are passed down through generations Problem with his theory…he didn’t understand HOW

Charles Darwin Darwin was a naturalist that traveled on the HMS Beagle to the Galapagos Islands in the Pacific Ocean. He observed many different plants and animals to include giant tortoises and finches. He noticed that the birds had different shaped beaks and he hypothesized that this had something to do with their diet.

evolution Artificial Selection- process by which we select the best organisms to mate and produce offspring; we are selecting for specific traits Ex. Breeding dogs, cats, livestock, etc Struggle for existence- there is regular competition for the resources (food, space, etc.) necessary for living which leads to the concept of… Survival of the fittest- only the organisms who have the traits that make them better suited for their environment will survive, reproduce and have offspring that survive.

Evolution Natural selection- a.k.a., survival of the fittest, “nature” (the environment) will “select” the organisms that will survive through the challenges they face day-to-day. Descent with modification- generations are modified from their ancestors due to natural selection

Theory of natural selection Variation exists within a population Variation is inherited Resources are limited More organisms are produced than will survive The organisms that are best suited for the for the environment will survive and produce offspring.

Support of Darwin’s Theories 1. Fossil record 2. Geographic distribution of living things 3. Homologous body structures 4. Vestigial Structures 5. Similarities in embryology 6. Biochemical similarities

1. FOSSIL EVIDENCE The fossil record shows that life HAS changed over time, Fossils: remains of organisms that lived in the past Ex. Imprints/bones/teeth/preserved insects Form in sedimentary rock and the weight of the subsequent layers turns the organisms into rock Indicate change (see what organism looked like then compared to now; see organisms that lived in past but no longer exist today

Older fossils will be deeper in sediment Layers are deposited over time on top of the older layer Fossils show that organisms have evolved from SIMPLER organisms (bacteria, invertebrates) in the lower layers to more COMPLEX organisms (vertebrates: fish…reptiles…mammals) in the upper layers EX: a magnolia (flowering plant)would be younger than a fern A squid (invert) would be older than a lizard (reptile)

EVIDENCE FROM FOSSILS How has the horse changed over time? How would studying the fossil evidence of the horse support the theory of evolution? The fossil evidence shows that the horse has changed over time in height, teeth structure, and bone structure

What would this fern fossil tell us about climate? This fossil was found in Antarctica. How could Antarctica have the type of climate suggested by this fossil evidence? If it had been closer to Equator; Pangaea Antarctica must have been a warmer climate; ferns are tropical plants

Dating Relative dating- age of the fossil is determined by comparing it to stratified rock around it. Absolute dating- provides a fairly precise date; uses radioactive elements, also known as carbon-14 dating Uses the half-life of the element- this is the amount of time it takes for half of the sample to decay

2. Geographic distribution Geographic distribution of living things- similar but unrelated species These 2 crocodiles were found on separate continents.

3. Homologous body structures Homologous body structures- these are structures that are built the same but may be used differently Suggests common ancestry Ex. The wing of a bird and the arm of a human

HOMOLOGOUS STRUCTURES Leg of dog Arm of human Wing of bird Flipper of whale All have similar bone structure, but the function is different (leg-walking; arm-carrying; wing-flying; flipper-swimming) EXAMPLES

4. VESTIGIAL STRUCTURES Structures present, but have no purpose Structures that are incomplete The presence of these structures indicates the structure once had a purpose (support for evolution) EX: femur/ pelvis in whales, appendix in humans

Vestigial Structures in Humans

5. EMBRYONIC similarities EMBRYO: early stage of development of living things Many organisms look similar very early in their development More stages similar… the more closely related they are Suggests common ancestry (note how similar these different organisms are in early stages)

6. BIOCHEMICAL EVIDENCE BIOCHEMICAL evidence is referring to similarities in DNA, proteins, amino acids, enzymes, etc. The more similar these compounds are in different organisms, the more closely related they are Suggests common ancestry BIOCHEMICAL SIMILARITIES OF ORGANISMS Comparison of Organisms % substitutions of amino acids in Cytochrome C Two orders of mammals 5-10 % Birds vs. mammals 8-12 % Amphibians vs. birds % Fish vs. Land vertebrates % Insects vs. vertebrates % Algae vs. animals 57 %

Biochemical Evidence We are most similar/ most closely related to chimp least similar/ closely related to chicken Hedgehog is most similar to mouse… based on the closeness of the DNA similarities…3% difference

Natural Selection How does natural selection result in a new species? Variation in a population comes from sexual reproduction and from different types within the species mating. Gene pool- all genes that are present in a population

Natural Selection & Polygenic Traits Directional Selection- individuals at one end of the curve have a higher fitness than those at any other position Stabilizing selection- individuals in the middle have a higher fitness Disruptive selection- individuals at the ends have a higher fitness than those in the middle

Genetic Drift A random change in genetic frequency. Just by chance some organisms will produce more offspring than others; this can lead to a trait becoming more common in the population.

Forming New Species What can lead to the formation of a new species? Behavioral isolation- 2 populations do not mate because of differences in courtship behavior, vocalizations, etc. Geographic isolation- 2 populations do not mate because they are separated by a physical barrier Immigration and emigration- individuals are introduced to a new location and are allowed to mate Migration- similar to immigration and emigration; just occurs seasonally and may not result in new mating partners

Patterns of evolution Divergent evolution (adaptive radiation)- a single species evolves into many through a variety of changes in the environment Supported by DNA and/or protein structures Ex. Monkey foot and human foot Convergent evolution- different organisms become more alike over time due to being in the same environment Supported by homologous structures Ex. Bird wing and bat wing Co-evolution- organisms need each other for survival therefore will evolve together Ex. Bumblebees and flowers