Lecture 1+2 (Bio-2040)

Biodiversity

variation, which within animals, is hard to grasp and understand. this is made sense by the scientific method

who theorized evolution by natural selection

Wallace and Darwin

E.O Wilson

The first naturalist to use biodiversity

Wallace

• went to the Amazon River to study biodiversity

• had a large collection of unknown bugs and other species, but lost most of them

The wallace line

named to show the drastic change in diversity overseas after Wallace travelled to Indonesia, this was the first of many contributions to biogeography

Darwin

Travelled the world, starting in South America (Galápagos Islands). Despite being sick, he worked on two ideas taken from economics and geology

• How can we explain the species difference between the mainland and the Galapagos Island

• How can we explain the differences among islands

Lyell

The man behind geological gradualism. The formation of mountains follows a gradual/uniform process of change over a long period of time.

malthus

The man behind ideas on economics and human population growth. investigated the idea of why human growth couldn’t be sustained over time.

Darwins proposal of evolution

It was not easy. Society was not ready for this, and the church did not accept this idea at all. The scientific community had the questions:

• The theory didn’t explain the origin of changes

• The theory didn’t explain how changes were passed along generations.

Darwin couldn’t explain these, and the answers wouldn’t come until years later

Mendell

researched chromosome heredity. His findings were only recognized 35 years later

Darwin’s theory of perpetual change

Living organisms are not constant or immutable; they change. Examples through fossil records, the effect of pesticides on insects and disease tolerance. This was widely accepted.

Challange of fossil records

Many are incomplete or biased

Darwins theroy of Common Decent

There is a common ancestor for all living forms. saw life as a branching tree. Introduction of homology and analogy.

Homologies

characters derived from a common ancestor. The differences arise from divergent evolution. ex. limb bones in vertebrates (same bone different use)

Analogies

Not from a common ancestor; independent origin. Similarities arise from convergent evolution. (different bone same use)

Cladograms

a nested hierarchy of groups in a branching diagram. tells when groups are related and how closely.

Gradualism

• change occurs as a continuous cumulative process over a long time.

Issues with the idea of gradualism

• mutations

• gaps in fossil records

  • Some say speciation is “sudden” and occasional

Natural Selection

Survival is differential and favours the fittest; the constant struggle for resources makes only the fittest reproduce and live. (survival of the fittest). Extreme cases can cause “mass extinction”

Pre-Cretaceous

When dinosaurs dominated the earth

Post-Cretaceous

Dinosaurs are gone, and mammals undergo adaptive radiation

Darwins theorys of speciation

• Perpetual Change

• Common Decent

• Multiplication of species

• Gradualism

• Natural Selection

Multiplication of species

When habitats change and allow one species to split into various species, having various derived forms brings the question of diversity in an area. Species are not easy to define.

Adaptive Radiation

The formation of various species from a common ancestral form

Typological Speciation

based on morphological similarity. Individuals who look the same are grouped together; this is the most classic concept.

Limitations of typological speciation

species change as they evolve

Biological Speciation

based on similarity, niche and the ability to interbreed and produce viable offspring. This is the most popular concept and relies on species to attract the best mate.

Limitations to biological speciation

hybrid creatures and species with asexual reproduction

Evolutionary Speciation

based on similarities, niche, ability to interbreed and evidence of ancestry.

Limitations of evolutionary speciation

species without ancestry information

Phylogenetic Speciation

based on similarities, niche, ability to interbreed, ancestry information and recognizable genetic variation from isolation.

Limitations of phylogenetic speciation

“recognizable variation” is hard to judge

Allopatric speciation

by spatial and temporal isolation (seperate/distant areas)

Sympatric Process

by niche specialization (coexistence/in the same area)

Formal recognition of a new species

1) an official name

2) an official description

3) an official type