Evolution

What is Evolution? Evolution is the theory that modern organisms have descended from ancient organisms. Evolution states that organisms change over time as a result of a change in the environment.

WHAT EVOLUTION IS NOT 1. It is NOT a fact... (it's a theory: a highly probable explanation affecting all biological phenomena, with much supporting evidence, and NO evidence against it). 2. It is NOT something one should believe in...(it's based on science, not faith).

WHAT EVOLUTION IS NOT 3. It is NOT concerned with the origin of life... (only the origin of species). 4. It is NOT just concerned with the origin of humans... (no more nor less than any other species). 5. It was NOT discovered or first explained by Charles Darwin... (many other people proposed the general idea long before Darwin did).

WHAT EVOLUTION IS NOT 6. It is NOT the same as natural selection... (natural selection deals with how evolution can take place; this idea was first proposed by C. Darwin). 7. It is NOT something which happened only in the past... (it's still going on...) 8. It is NOT something which happens to individuals... (it happens to populations).

WHAT EVOLUTION IS NOT 9. It is NOT an accidental or random process... (there are built-in limits and constraints; it is influenced by both historical circumstances and environmental factors).

Charles Robert Darwin

Darwin Darwin is the man who came up with the Theory of Evolution. In 1831 he went to different remote islands called the Galapagos Islands. The trip lasted for 5 years. 30 years later he actually published a book on his theory of Natural Selection.

Galapagos Islands

Galapagos Island diversity The diversity of living species was far greater than anyone had previously known!! Each island had its own type of tortoises and birds that were clearly different from other islands These observations led him to develop the theory of evolution!!

Galapagos Turtles

Galapagos Finches

Darwin’s Theory Individual organisms have variations (differences) which can be passed to offspring. More organisms are born than can survive. Organism compete for limited resources such as food and a place to live.

Darwin’s Theory Organisms that are best suited to the environment survive, reproduce, and pass their good traits to their offspring. This natural selection causes populations to shift over time. Species that are alive today came from ancestors that were best suited for their environment.

1. Individual organisms have variations Compare your brothers and sisters. They have a lot in common, but they also have differences. These differences are called variations. Consider a set of offspring from a pair of frogs: Some of the offspring might have a stickier tongue than the others.

2. More organisms are born than can survive. Example: A frog can lay 200 eggs, yet not all eggs will survive to become adult frogs.

3. Organism compete for limited resources There is not enough food, water, space, etc. for all the offspring of a pair to survive. To stick with our frog story, let’s say that the frogs have to compete for flies. There aren’t enough flies for everyone.

4. Survival of the most fit! Put it together… there were too many frogs for them all to survive, there was variation in the frogs, like some had stickier tongue than the others, and, there’s not enough flies for all the frogs to eat. So, who do you think would survive the best? The frogs with the stickier tongues who could catch flies better, or the frogs without sticky tongues who could not catch flies as well?

5. Ancestors produce new species Then, if genes controlled the trait for sticky tongues, what type of offspring would these frogs produce? Ones with sticky tongues!! Soon a lot of the population of frogs would have sticky tongues. “

Evidence of Evolution Darwin argued that living things have been evolving on Earth for millions of years. Evidence for this process include: the fossil record geographical distribution homologous structures similarities in early development, or embryology.

The Fossil Record  Darwin saw fossils as a record of the history of life on Earth. By comparing fossils from older rock layers with fossils from younger layers, scientists could document that life on Earth has changed over time.

Some Evolution Definitions Fossils-preserved remains of ancient organisms. Usually, the deeper down the fossil is, the older it is. Scientists also use radiometric dating, like carbon dating or C-14 dating, to determine the age of fossils.

Geographic distribution Organisms adapt to different parts of the world because of the different environments Some organisms can be very similar because they live in similar environments without being related.

Geographical Distribution Similar, But Unrelated Species

Homologous Body Structures Structures that have different mature forms but develop from the same embryonic tissues are called homologous structures. These structures are similar but may have different functions such as walking, swimming, and flying.

Homologous Body Structures

Similarities in Embryology In their early stages of development, fish, reptiles, birds, and humans look similar, providing evidence that they shared a common ancestry and are related.

Similarities in Embryology

Some Evolution Definitions Natural Selection-The traits that help an organism survive in a particular environment are “selected” in natural selection

Some Evolution Definitions Adaptation- any inherited characteristic that increases an organism's chance of survival.

Examples of adaptations Camouflage

Examples of adaptations Long necks

Examples of adaptations Big ears for cooling

Some Evolution Definitions Population-A population is a group of individuals of the same species that interbreed.

Some Evolution Definitions Gene pool-A gene pool consists of all genes, including all the different alleles, that are present in a population.

Some Evolution Definitions Speciation- Speciation is the formation of new species. Species-A species is a group of organisms that breed with one another and produce fertile offspring. fertile offspring-babies that can have babies

What factors are involved in the formation of a new species? The gene pools of two populations must become separated for them to become new species. Species form from Reproductive isolation Behavioral isolation Geographic isolation Temporal isolation

Reproductive isolation As new species evolve, populations become reproductively isolated from each other. When the members of two populations cannot interbreed and produce fertile offspring, reproductive isolation has occurred.

Reproductive isolation Tigon Result of male tiger and female lion mating in captivity. Offspring are infertile. Separated both geographically and reproductively in the wild. .

Reproductive isolation Liger Separated both geographically and reproductively in the wild. . Result of male lion and female tiger mating in captivity. Offspring are infertile.

Behavioral isolation Behavioral isolation occurs when two populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior.

Geographic isolation Geographic isolation occurs when two populations are separated by geographic barriers such as rivers or mountains.

Temporal isolation Temporal isolation occurs when two or more species reproduce at different times.

The End