Charles Darwin: Father of Evolution

EVOLUTION Charles Darwin  Very important Biologist!!! (Father of Evolution)  Responsible for the Theory of Natural Selection  Wrote book: The Origin of Species Evolution is supported by fossil evidence happens when species change over a long period of time in response to their environment only occurs when the gene pool changes is influenced by the mechanism of Natural Selection

4 Principles for the Theory of Natural Selection 1. Organisms produce more offspring than can survive 2. In any population, individuals have variations of traits 3. Individuals with certain favorable traits survive in the envrironment and pass those traits on. 4. Over time, offspring with certain favorable traits (variations) will make up most of the population and ultimately look different from their ancestors.

Darwin’s Studies Upon the HMS Beagle as a naturalist, he collected both biological (live) and fossil specimens and found them to be quite diverse. He tried to find possible relationships among these specimens. Galapagos Islands- studied many species of plants and animals and found them to be unique to the islands and yet similar to species found elsewhere.

Darwin’s Studies Thomas Malthus helped support Darwin’s theory by indicating that human populations grow faster than the Earth’s food supply. He was describing competition for food, shelter, mates, space and ability to escape predators. Recognizing Natural Selection and its effect on populations also aided in his theory. But without knowledge of genetics, he was unable to really understand “why”.

Review of Terms Artificial Selection- breeding of organisms with specific favorable traits to produce offspring with those traits. (ex: show dogs and race horses) Species- a group of interbreeding organisms that can produce healthy, fertile offspring Population- a group of a species living together in one location

Adaptations- inherited characteristic that aids an organism's chance of survival in its environment. Structural adaptation - physical features of an organism that help the species survive (big teeth, claws, thorns)  Mimicry – one species that is not harmful but has a close external resemblance to one that is OR when several species look the same and they are all harmful.  Camouflage – species that can disguise, hide, or deceive a predator. Camouflage and mimicry can cause populations to increase over time. Physiological adaptations – can occur in only some individuals and occurs more quickly. (resistant bacteria, roaches, weeds)

4 Evidences of Evolution 1. Fossils- provide a record of early life even though fossil records are incomplete. The fossil record identifies organisms throughout the geologic time scale.

Archaeopteryx

2. Anatomy- structural similarities show organisms evolved from a common ancestor  Homologous structures- structural features with a common evolutionary origin. They are similar in arrangement and/or function  Analogous structures- structures that do not have a common ancestry, but have similar functions (not structure)  Vestigial structures- a structure that is still present, but is no longer needed or used. (tailbone, appendix)

The wings of pterosaurs (1), bats (2) and birds (3) are analogous: they serve the same function and are similar in structure, but each evolved independently. Analogous Structures

The Wings on Flightless Birds Hind Leg Bones in Whales Blind Cave Lizards The Human Appendix Wisdom Teeth in Humans Vestigial Structures

3. Embryology- earliest stage of growth and development. Shared features in embryos suggest evolution from a distant, common ancestor. Example: mammals, reptiles, birds and fish all have a tail and a pharyngeal pouch, but in fish the pouch develops into gills and in the others, it develops into ears, jaws and throat.

4.Biochemistry-(Biomolecules) : Proteins- amino acids Nucleic Acids- DNA and RNA Carbohydrates - sugars Lipids - Fats The fewer the differences in the amino acid sequence, the more similar their biochemistry.

Mechanisms of Evolution Populations, NOT individuals evolve Natural Selection acts on the phenotypes in a population Evolution occurs as a population’s genes and the allelic frequency changes.  gene pool- all the genes in the population  allelic frequency- percentage of each allele

Populations in genetic equilibrium are not evolving. Any factor that affects the genes in the gene pool can change the allelic frequency and cause evolution.

Mechanisms for Genetic Change: 1. Mutation- a change in hereditary information caused by radiation, chemicals, or simply by chance 2. Gene flow- change in the gene pool due to migration

Mechanisms for Genetic Change: 3. Genetic Drift- alteration of allelic frequency by chance 4. Natural Selection- changes in allelic frequencies due to inherited variations

Mutation, Gene Flow and Genetic Drift have a greater effect if the population is small. If the population is large, these have minimal effect.

Documented record of natural selection in the peppered moth. This study illustrates that a mutation must be present before the environment changes (illustrated by melanism preceding pollution by soot from the burning of soft coal, in England). Predators (birds) eliminated most of the conspicuous moths in each location, resulting in adaptive changes to match the environment in each location.

3 types of Natural Selection that act on variations: Stabilizing selection- favors the average individuals causing a decrease in variations Directional selection- favors one extreme over the other, which can lead to more rapid evolution. Disruptive selection- favors both extremes, resulting in no intermediate form which can cause the evolution of two new species

Evolution of Species Speciation:  Evolution of a new species  Occurs when members of similar species no longer mate within their environment.

Causes of Speciation: Geographic Isolation: mountains and streams force the population size to decrease and the organisms can breed only with each other. Reproductive Isolation: interbreeding organisms can no longer mate and produce fertile offspring.

These are all considered to be the same species, but different geographic subspecies, a common occurrence in widespread species. Although each geographical variant is phenotypically distinct, intermediates exist between the populations.

Reasons for Reproductive Isolation Because their genetic information has changed too much and fertilization can no longer occur. Behavioral- one population mates in the spring and the other mates in the fall Polyploidy- too many or too few chromosomes due to a mistake during Meiosis.

Evolutionary Time Gradualism- belief in a VERY slow evolution Punctuated Equilibrium- more rapid (10,000 years) evolution occurs as a result of some major environmental change that causes evolution to occur and then go through periods of equilibrium. Both of these theories are supported by fossil evidence

Three Types of Evolution Convergent Divergent Adaptive

Convergent Evolution Occurs when distantly related species look alike because they occupy similar environments in different parts of the world.

Divergent Evolution Occurs when closely related species have evolved to look different due to adaptations to a changing environment.

Divergent Evolution

Adaptive Radiation When an ancient species evolves into many different species in order to fit into several diverse habitats.

Terms Immigration - The movement of organisms to a specific area within the same geographical niche.  example - From an upstream aquatic environment to further downstream. Emigration - Pertaining to animals that are moving away from their natural environment into another geographical niche.

Coevolution Two or more species having a close ecological relationship evolve together such that one species adapt to the changes of the other, thereby affecting each other's evolution.  Example – Cheetah and the gazelle

Things to know Strongest evidence for evolution – DNA Natural Selection needs genetic variation and sexual reproduction to occur Variations of phenotypes comes from independent assortment Some evidences for evolution were gained from comparative biochemistry (insulin from cows was used in people because of its similarities).