Charles Darwin is known as the Father of Evolution.What we know now seems like common sense but in Darwin’s day, it wasn’t. So…..How did Darwin come up with his new and radical ideas that eventually led to the (controversial) Theory of Evolution?
After studying at Cambridge, Charles was recommended for a surveying trip on the HMS Beagle. He sailed around the world on the Beagle for 5 years, working as a naturalist.
On the voyage, Darwin noticed that everywhere he went, the animals and plants differed vastly. Yet, there were similarities Patterns in the species suggested that the species had changed over time and had given rise to new and different species.
Many of Darwin’s conclusions were based on observations of wildlife in the Galapagos Islands. The Galapagos Islands lie 500 miles west of Ecuador in the Pacific Ocean, directly on the equator. “Galapagos” means turtle.
Were the animals and plants created to match their environment? Then, why didn’t the Galapagos finches look like the birds of the African continent, since the environments of both the Galapagos and Africa were similar.
Darwin guessed that some of the birds from South America migrated to the Galapagos. Once on the islands, the birds must have changed over the yearsbecause each island was different from the others….landscape and flora.
Darwin concluded: Each species had descended, with changes, from other species over time. Darwin called this… Descent With Modifications or evolution (change in species over time)
The mechanism by which evolution takes place. Natural Selection …or Survival of the Fittest. Five basic components:
Nature has to have some variety in order to choose. Look around you…are you all the same? 1. All species have genetic variation.
2. Organisms produce more offspring than can survive. Many that survive do not produce offspring. The female green sea turtle lays a clutch of about 110 eggs. She may lay several clutches. It is likely that less than 1% of the hatchlings will ever reach sexual maturity.
food shelter water space mates 3. Since more organisms are produced than can survive, there is competition(struggle for existence). Competition exists WITHIN and AMONG species. Within and Among Species for And Within a Species for
Short-term natural disasters can have large impacts on competion. (drought, fires, floods, snowstorms, hurricanes, and tornadoes) Long-term changes in the environment also affect survival. (ice ages, biome shifts, global warming etc)
Fitness: the ability of an individual to survive and reproduce in its specific environment. Fitness is a result of adaptations. 1st He who spreads the most genes wins! 4. Survival of the fittest Some organisms are more suited to their environment as a result of variations in the species. Individuals that are fit to their environment survive and leave more offspring than those who aren’t.
Over time, genes for less favored characteristics will be eliminated from the gene pool. Example: giraffes and their increasingly longer necks. 5. Descent with modification: Living species today are descended with modifications from common ancestral species that lived in the past. Characteristics of fit individuals increase in a population over time.
the variation has to already exist. If the environment changes. the variation may give an advantage to survive environmental change. Natural Selection: Survival of the Fittest An adaptation is any inherited characteristic (a genetic variation) that can increase an organism’s chance of survival. An organism does not change because of the need or desire to survive. The organism is either born with the variation that enables it to survive or it dies.
Darwin published his theory in the book November 24, 1859 On the Origin of Species And that is why Darwin is the father of Evolution
Natural Selection in Action • Camouflage (Cryptic coloration)
Natural Selection in Action • Mullerian Mimicry –untasty imitates untasty ….both benefit by making sure their predators gets the point. • Monarch and Viceroy Butterfly
Natural Selection in Action • Batesian Mimicry – palatable (tasty) mimics unpalatable (untasty) • Coral vs. King Snakes: Red on yellow, kill a fellow, red on black friend of Jack
Natural Selection in Action • Warning Coloration (Aposematic coloration)
Natural Selection in Action • Disruptive Coloration
Natural Selection in Action • Counter Shading
Natural Selection in Action • Eye spots
Things to remember: a. Populations evolve, not individuals. b. Natural selection is the mechanism of evolution. c. Evolution occurs by chance (NOT GOAL ORIENTED). d. Organisms are born with adaptations, they can’t adapt because they need or want to Evolution
Part II • Speciation • Causes of evolution • Rates of evolution
An organism that has the potential to interbreed in nature and produce viable, fertile offspring that looks like their parents. Species Speciation is the creation of a new species
Occurs when 2 pop. are capable of interbreeding but have different courtship rituals or other reproductive strategies that involve behavior Speciation Two or more species reproduce at different times results from Reproductive Isolation results from Isolating mechanisms which include Geographic isolation Behavioral isolation Temporal isolation produced by produced by produced by Physical separation Behavioral differences Different mating times which result in Two pop. Are separated by geographic barriers such as rivers, mountains, or bodies of water Independentlyevolving populations which result in Formation ofnew species
A reproductive barrier is any factor that prevents two species from producing fertile hybrids, thus contributing to reproductive isolation. Habitat/Geographical Isolation Temporal Isolation Behavioral Isolation Mechanical Isolation Gametic Isolation Reproductive Barriers
Mutations - random changes in genetic material at the level of the DNA nucleotides or entire chromosomes Natural Selection- most important cause of evolution; measured in terms of an organism's fitness Causes of Evolution • The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals…the more fit, the more they contribute.
Modes of Selection (types of natural selection) a. Stabilizing Selection- average phenotypes have a higher fitness over the extreme phenotypes b. Directional Selection- phenotype at one extreme has a higher fitness over the average and the other extreme c. Disruptive Selection- both extreme phenotypes have a higher fitness than the intermediate phenotypes
Original population Frequency of individuals Evolved population Phenotypes (fur color) Original population These mice have colonized a patchy habitat made up of light and dark rocks, with the result that mice of an intermediate color are at a disadvantage. If the environment consists of rocks of an intermediate color, both light and dark mice will be selected against. In this case, darker mice are favored because they live among dark rocks and a darker fur color conceals Them from predators. Modes of Selection Disruptive Directional Stabilizing
3. Mating Preferences- Organisms usually do not choose their mates at random, thus the selection process can cause evolution 4. Gene Flow- Transfer of genes between different populations of organisms. This situation leads to increased similarity between the two populations (Tends to reduce differences between populations over time) 5. Genetic Drift (Founder Effect & Bottleneck)- Situation that results in changes to a population's gene pool caused by random events, not natural selection. This situation can have drastic effects on small populations of individuals. Common on islands. Causes of Evolution
Part III: Types of Evolution Extinction
1. Divergent Evolution- Multiple species of organisms descended from the same common ancestor at some point in the past. Method of evolution accounting for the presence of homologousstructures. Adaptive Radiation. Ex. Darwin’s finches Types of Evolution
2. Convergent Evolution- Because certain adaptations are more advantageous in different environments, unrelated organisms that live in similar environments will have similar features that perform similar functions. • Method of evolution accounting for the presence of analogous structures. • Ex. Dolphins and shark
3. Coevolution–Organisms that are closely connected evolve together. • Method of evolution accounting for specialists. • Ex. Monarch butterfly and milkweed plants • Insects and flowers
Extinction As the environment changes, organisms must have variations (adaptations) that will determine whether they can survive with the changes or they can’t and they die. If an entire species cannot adapt, that species will then become extinct. No More, Finished, Bye-Bye!
Mass Extinction There have been at least 5 MASS extinctions during Earth’s history where a huge % of the living species were destroyed