chapter 18 Evolution and origin of species

Evolution

The process of adaptation through mutations which allow desirable characteristics to be passed to the next generation

1749-1788 Buffon

Observed that different geographic regions have different plants and animals even if the environments were the same. Some scientists at this time accept that there were extinct species.

~1768 Hutton

Stated that geological change occurs gradually by the accumulation of small changes

1801 Lamark

Published a book detailing a mechanism for evolutionary change. Stated the modification happened in an individual due to use or disuse of the structure and then it was passed onto its offspring.

Evolutionary change

The inheritance of acquired characteristics is due to the environment causing modifications

1830 Lyell

Popularized Hutton’s view. He explained weathering cause erosion which uncovered fossils, and that the earth was old enough to allow gradual change in species

4.5 Billion years

How old is earth

1831 Darwin and 1858 Wallace

Both INDEPENDENTLY convinced and described the mechanism for evolution and each spent significant time exploring the natural world

Natural Selection

The reproduction of individuals with favorable traits that survive in environmental change because of those traits

Artificial selection

When humans selectively breed organisms with desirable traits

List Factors of Artificial Selection

1. Characteristics are inherited or passed from parent to offspring

2. Not offspring are produced than are able to survive

3. Resources for survival and reproduction are limited

4. There is competition for limited resources

5. There are inherited variations among offspring, offspring with the variations that allow them to win the competition will survive and have more offspring with the winning variation

Mutations and Sexual reproduction

Genetic variations in a population come from what 2 things?

Adaptation

An inherited variation that allows an organism to survive and reproduce

Evidence of Evolution

1. Fossils

2. Comparative anatomy

3. Biogeographical distribution

4. Molecular homologies

Fossils

The remains of organisms between 10,000 and billions of years ago

Fossils ex.

Shells, bones, teeth, trace (trails, foot prints, burrows, casts, preserved droppings, plant impressions), organisms preserved in ice, and insects in resin

Comparative anatomy

Similarities between organisms includes:

1. Homologous structures

2. Analogous structures

3. Vestigial structures

4. Embryology

Homologous structures

Anatomical similarities (arms)

Analogous structures

Structures that have the same function but are not anatomically similar (wings)

Vestigial structures

Organs that a fully developed in one group, but are reduced or nonfunctional in a similar group (nictitating membrane)

Embryology

Similar patterns of development (all vertebrate embryos have a postanal tail and pharyngeal pouches)

Biogeographical distribution

The distribution of organisms throughout the planet due to plate tectonics forming oceans, rivers, mountains, islands, wind and current patterns. Barriers are then formed between the organisms to evolve to their environment separate from each other

Molecular homologies

Similar molecules in all living cells

1. All cells contain the same biomolecules- carbs, lipids, proteins, nucleic acids

2. There are similar genes and proteins in different species

3. There is similar developmental genes in different species (hox genes)

the evolutionary species concept

Every species has its own evolutionary history. We use specific traits to distinguish one species from a different species

The biological species concept

Focuses on reproduction, organisms are the same species if they can reproduce and make fertile offspring

Species

Group of individuals that interbreed and produce fertile, viable offspring in nature

Speciation

The splitting of one species into 2 or more different species or the transformation of 1 species into a new species

Reproductive isolation

Organisms are separated into 2 or more groups and Connor or will not reproduce

3 types of mechanisms that can cause reproductive isolation in a population

1. Prezygotic isolation

2. Postzygotic isolation

3. Geographic isolation (allopatric speciation)

Prezygotic isolation

Before the formation of the zygot by stopping reproductive attempts or preventing fertilization

5 forms of Prezygotic isolation

1. Habitat isolation

2. Temporal isolation

3. Behavioral isolation

4. Mechanical isolation

5. Gamete isolation

Habitat isolation

Species occupy different habitats

Temporal isolation

Species reproduce at different times

Behavioral isolation

Species have different cordship patterns

Mechanical isolation

Reproductive parts are not compatible

Gamete isolation

Gametes are exchanged but do not form a zygote

Postzygotic isolation

After the formation of a zygote, 2 different species mate and create offspring

Three possible outcomes of Postzygotic isolation

1. Zygote mortality

2. Hybrid sterility

3. F2 fitness

Zygot mortality

The zygote is not viable and dies

Hybrid sterility

The zygote develops but is a sterile adult (cannot have offspring of its own)

F2 fitness

The zygote develops and reproduces, but its offspring cannot reproduce

Geographic isolation (allopatric speciation)

Separation due to a physical barrier

List of geographic isolation

1. A population is together and have gene flow (reproducing and making fertile offspring)

2. A barrier occurs between the population separated it into 2 separate groups

3. Genetic drift and natural selection causes differences between the two populations (differences in their gene pool)

4. After a significant amount of time the two different populations will not/cannot reproduce forming 2 different species