Mechanisms of Evolution. Members of the same species : Can reproduce in a natural setting and produce fertile offspring. Background terms. A horse and donkey can mate in the barnyard to produce a mule. The mule is a very strong, hardworking animal (albeit stubborn!), but alas,
Members of the same species: Can reproduce in a natural setting and produce fertile offspring Background terms
A horse and donkey can mate in the barnyard to produce a mule. The mule is a very strong, hardworking animal (albeit stubborn!), but alas, mules cannot have babies. Are horses and donkeys members of the same species? No – the mule cannot reproduce, therefore is not fertile. Apply species definition
Are all birds members of the same species? Think of the biggest and smallest birds you can imagine. Certainly hummingbirds cannot mate with ostriches! More species defined
Are all domesticated dogs members of one species? Can all dogs mate (theoretically)? Are all normal puppies fertile? Yes. All dogs are members of one species: Canisdomesticus More species defined
A lion and tiger can be artificially mated together in a zoo. This produces a “liger” Are lions and tigers therefore members of the same species? No, they didn’t mate in a natural setting – and never would – they don’t even live on the same continent! More species defined
Branching diagram (CLADOGRAM) Shows changes in species over time Each new branch represents a newly evolved feature Evolution vocabulary
Which organisms have jaws? Which organisms have claws or nails? Is the salamander more closely related to the perch or pigeon? CLADOGRAMS
MORE CLADOGRAMS Where in the image is now? Left, right, top or bottom?
Cladogram showing fish evolution Where is the common ancestor?
CLADOGRAM OF DINOSAURS • If a line stops before the top, what does that mean?
CLADOGRAM SHOWING EVOLUTION OF BIRDS FROM DINOSAURS What is the common ancestor?
MORE CLADOGRAMS - SIDEWAYS Where is NOW in these diagrams?
Evolution: changes in species over time • Speciation: the formation of new species • Gradualism: the theory that species changed very gradually over time. Fossil evidence shows jumps, but the hypothesis is that we simply haven’t found the in-between fossils (missing links). • Punctuated equilibrium: The theory that species are relatively unchanged for long periods, but then go through sudden rapid changes and new speciation, usually due to geographic isolation or environmental pressures. Mechanisms of Evolution - vocabulary
Gradualism vs. punctuated equilibrium Evolution - vocabulary
Natural selection: (aka Survival of the Fittest) The members of the species that are best adapted to the environment will survive to pass their genes on to the next generation. The less well adapted will be more likely to die before reproducing, reducing the proportion of their particular set of alleles in their population. The “environment selects” which members survive. Mechanisms of Evolution
Fittest doesn’t necessarily mean strongest or fastest • Competition is not usually direct • Fittest = best adapted • Adaptations: • Camouflage • Mimicry • Structure • Different Teeth shapes for different foods • Beak shapes (as in lab) • Leaf color • Seed dispersal • Attractiveness for mate • Attractiveness for pollinators • Ability to withstand a freeze, or draught, or flood or ….. • Can you come up with some? Mechanisms of Evolution
During an especially cold winter, the birds with the most under-feathers (down) are more likely to survive, while some the others will die off. The “environment selects” the survivors, who then pass on their genes to the next generation. Examples of natural selection
Slower sea turtles may be eaten by gulls before fast ones, when trying to get to the ocean. The fast ones pass their genes on to produce fast offspring. Examples of natural selection
A strong species is one in which there are many differences, or variations, between individuals in the population. These variations allow individuals to survive changes in the environment, and multiple situations. Not all members survive, but the species does. Mechanisms of Evolution –Genetic Variations
Ex: The faster turtles on land may attract more attention from gulls, and may also be slower swimmers. Slow, better camouflaged ones may swim better and have higher chance of survival from predators once in the water. Both variations are important to the species. Mechanisms of Evolution – Variations examples:
Not all members of a population are susceptible to the same illnesses, or they would all die from the same disease. Clones, which have identical genes, are all strong in the same areas and weak in the same areas. One event (drastic environmental change, new germ, loss of particular food source) could kill them all at once. Mechanisms of Evolution – Variations examples:
Irish potato famine in 1843. Due to LACK of variation Cloned potatoes all succumbed to one single fungus species, that wiped out the whole potato crop for two years, starving 1 million. Mechanisms of Evolution – Variations examples:
Many species purposely produce more offspring than they know will survive This introduces competition, so that only the members with the best adaptations survive and the less well adapted die off. The less adapted may have survived if they didn’t have to compete with so many others Mechanisms - overproduction
Overproduction examples Frog eggs
Overproduction examples Maple seeds
Antibiotics kill bacteria Bacteria usually reproduce by binary fission, whichisbasically mitosis => genetically identical offspring But when the species is threatened, (as when their environment changes with antibiotics) they can swap DNA through a conjugal bridge. Evolution in action: Antibiotic resistance
Evolution in action: Antibiotic resistance • When bacteria conjugate, this introduces genetic variation, and gives the species a chance to develop a variation that does not get killed by the antibiotics
Evolution in action: Antibiotic resistance • So if you don’t finish all your antibiotics, the strongest few could be left behind to multiply. • Then if you get sick again, you will need a different, stronger antibiotic to kill the stronger bacteria. • The bacteria have evolved, by natural selection, to survive the environmental pressures in your body
Evolution in action: Antibiotic resistance • New species of bacteria evolve every day • Forcing the medical profession to constantly have to continue to develop new drugs to kill them • This “arms race” has led to “super-bugs” • such as a new strain of TB that is killing thousands and cannot be treated with antibiotics.
The few insects of a species that survive reproduce, passing the survival genes down Eventually, most of the population is unaffected by the pesticide so that the pesticide eventually is rendered useless, and the insect population is even stronger. The arms race continues Evolution in action: Pesticide resistance
Fossils Evidence for evolution
evidence coprolite Mosquito in amber Dino tracks - Utah
Homologous structures • Similar structures with different functions Evidence for evolution comparative anatomy
Analogous structures • Structures are different, but functions are similar Evidence for evolution – comparative anatomy
Vestigial structures – no longer needed Evidence: comparative embryology Snake pelvic bones Goose bumps Whale pelvic bones
Embryonic comparison evidence
Biochemical comparisons • The more similar the DNA, the more recently two species branched apart. • Many other chemical processes are similar among species. • Soft tissue found inside fossilized dinosaur bones was found to have strikingly similar protein structures as those in chickens! evidence Can you see it?
Fossil evidence from different continents fit together where continents fit together before Pangea broke up EVIDENCE – GEOGRAPHIC DISTRIBUTION
Earth formation 4.6 BYA • Swirling ball of hot molten lava • Gravity pulls in heavy solid nickel core • Magma begins to cool into thin crust • Rain begins to fall • Harsh, hot, toxic, anaerobic (no free oxygen in atmosphere) Overview of evolution
First life: archaebacteria – • prokaryotes • Don’t need oxygen • Don’t produce oxygen • thrive in harsh environments like deep ocean vents & hot caustic puddles at Yellowstone First 4 billion years
Next life: photosynthesizing prokaryotes • Cyanobacteria • Make oxygen – for a billion years First 4 billion years
Finally: single-celled eukaryotes • (have nucleus and membrane-bound organelles) • Endosymbionttheory = photosynthesizing prokaryotes were absorbed by other bacteria to become the first organelles - chloroplasts First 4 billion years - From Prokaryotes to eukaryotes Eukaryotic cell
Soft-bodied Multi-celled eukaryotes • Began as colonies of single-celled organisms. • Cells started to specialize and organize into multicellular organisms • No backbone yet • jelly fish, • sponges, • Worms • seaweed First 4 billion years
Cambrian explosion Adaptive radiation: rapid speciation due to new opportunities Once life organized, and the planet was a comfortable living space, evolution happened in leaps and bounds, with new species diverging, rapidly filling every niche Next .5 billion years (about 500 MY)
Mutations • Some good, improve survival, so get passed down • Mixing of genes through sexual reproduction • Genetic “drift” • Driven by Natural Selection • Punctuated equilibrium • Gradualism • Adaptive radiation • Remember…it took billions of years to get this way! Evolve how?
Spontaneous generation – living things can arise from non-living things • Based on pure observation • Flies come from meat • Bacteria comes from broth • Frogs comes from rain! Evolution of evolutionary theory
Biogenesis – living things come from living things • Break down the term • Bio = life • Gen = birth, origin • Francesco Redi 1668 • Disproved spontaneous generation by setting up simple experiment to show covered meat produces no flies Evolution of evolutionary theory
Jean-Baptiste Lamarck – theory of natural selection: • Organisms can change their genes through their behavior • Charles Darwin - theory of natural selection • HMS Beagle – • voyage to Galapagos Islands 1830’s • Helped form ideas of speciation by geographic isolation from observations of species on mainland verses different islands Evolution of evolutionary theory