Evolution The Unifying Theory of Zoology

Contemporary Scientific History of the Universe billion years in 30 volumes - each volume = 450 pages -each page = 1 million years Big Bang, p. 1 Origin of Earth Life BeginsComplex Animal Life Dinosaurs pp Modern Humans p. 450, last sentence

What is Evolution?

Evolution = Descent with Modification Species originate as modified descendants of other species. Biological evolution is the origin of new species from previously existing ones over time.

“As many more individuals of each species are born than can possibly survive, and as consequently there is a frequently recurring struggle for existence, it follows that any being, if it vary in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of survival and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form.” Charles Darwin, The Origin of Species

Darwin’s Theory If there is a struggle for existence… If heritable variations exist among members of a population… If these variations affect survival and/or reproduction… Then species will change over time.

There is a struggle for existence. Species tend to produce more offspring than the environment can support. Darwin calculated that even one slow-breeding female elephant could give rise to 19,000,000 elephants after 750 years if all of her young survived and reproduced at the same rate. Obviously, the environment cannot support all elephants that are born.

Heritable variations exist. An impressive amount of variation exists within living species. Breeders of animals and plants use these diverse characteristics to establish new varieties of dogs, cats, pigeons, wheat, cotton, corn, and other domesticated organisms.

Variations affect survival & reproduction. Certain individuals possess inherited traits that make them more likely than other individuals to survive and/or reproduce. “Differential survival and reproduction”

Bears  Colored for their terrestrial environment  Poor swimmer  Herbivore  Excellent climber  Low endurance  Colored for their arctic environment  Excellent swimmer  Carnivore  Poor climber  High endurance

Species will change over time. Evolution in Action

Populations evolve, not individuals. Individuals may change throughout their lifetimes, but this is not evolution. Evolution occurs across many generations. Over time, populations acquire new characteristics that enhance their ability to survive and/or reproduce in a given environment.

Variations are “Random” Mutation and sexual recombination occur randomly. The variations that occur do not anticipate the “needs” of the organism. In this sense, “random” does not mean that anything can happen.

Natural Selection is NOT Random Genetic variation occurs randomly, but natural selection is NOT random. Genetic variations that aid survival and reproduction are more likely to become common than variations that do not. Nature imposes a direction to evolutionary development. Though dolphins are more closely related to humans than they are to sharks, they have evolved bodies adapted to an aquatic environment.

Evolution is About Consequences Evolution is historically contingent; that is, “windows of opportunity” constantly open and close. Once certain changes have occurred, the range of possible future changes is permanently altered.

“Windows of Opportunity” The earliest turtles could not retract their necks. Proganochelys 220 million years ago Proganochelys 220 million years ago side neck turtles (southern hemisphere) side neck turtles (southern hemisphere) vertical neck turtles (northern hemisphere) vertical neck turtles (northern hemisphere) Later, two distinct forms of neck retraction evolved. With the extinction of the turtles that could not retract their necks, the possibility that another form of neck retraction would evolve was lost.

Evolution is Predictive Tiktaalik roseae Ichthyostega Eusthenopteron Panderichthys Acanthostega Tiktaalik 385 million years ago 365 million years ago ? ?

Conclusion “Nothing in Biology makes sense except in the light of evolution.” Theodosius Dobzhansky ( )

EVOLUTION and ECOLOGY The Big Picture – Putting the Pieces Together

Biomes Many biomes in the earth: –Grassland –Tundra –Taiga –Rainforest –Deciduous Forest Through evolution, animals adapt to live in different biomes or ecosystems.

Populations A population is a group of organisms in a species. A community is a group of populations living in an ecosystem. Ecosystems vary based on biotic (living) and abiotic (nonliving) factors.

Populations Animals in a population will have competition for resources. –Food –Shelter –Water –Space –Mates

Limiting Factors When resources are limited, competition gets more intense. Limiting factors are a form of environmental resistance that limits population size. Is limited population a good thing?

Biodiversity More populations living in an ecosystem causes BIODIVERSITY. Biodiversity means more genetic variation = increased likeliness for new species to develop Certain biomes allow for more diversity than others: –Rainforest –Coral Reef

Biodiversity Biodiversity drives EVOLUTION Biologists most often define biodiversity as the "totality of genes, species, and ecosystems of a region". –species diversity –ecosystem diversity –genetic diversity

Natural Selection With more variation, some animals will be better fit for their environment than others. Survival of the fittest This causes “natural selection” –gradual, non-random process by which biological traits become either more or less common in a population as a function of reproduction from their bearers

Same species = may have better fitness in different ecosystems The environment (nature) will change, and the animal that will adapt best to those changes will be the one that survives and reproduces. Natural Selection

Loss of Biodiversity Rapid environmental changes typically cause mass extinctions. –Human impact is now a contributor One estimate is that less than 1% of the species that have existed on Earth are extinct. Extinction – the death of a species –those genes are now absent from the gene pool

Symbiosis Animals are dependent on others in their community. They all are “pieces” in the giant “puzzle” that is an ecosystem. As animals evolve in their specific environments, complex relationships form between species. We call this SYMBIOSIS.

Symbiosis There are 4 types of symbiotic relationships. –Predator/Prey Relationships: The hunters and the hunted.

Symbiosis –Mutualism: relationship where both species benefit (+/+)

Symbiosis –Commensalism: relationship where one species benefits (+/0)

Symbiosis –Parasitism: relationship where one species benefits and the other is harmed (+/-)