2 types of evolution

Macroevolution• Changes beyond the species

• Examples: - Biogeography- Fossil record- Homology- Biochemical similarities- Chromosomal similarities

Microevolution• Changes within a gene pool

• Examples: - Kettleworth moths- Insect resistance- Drug resistance

Let’s do Macroevolution first

1. Biogeography: the geographic distribution of species

• Why does the Arctic have polar bears and Antarctica penguins?

• Why are most of the species on islands more closely related to species on the nearest mainland.

• The answer is that modern species are where they are

because they evolved from ancestors that inhabited those regions.

• In the case of island species, inhabitants must have migrated from the original, mainland area where the species originated.

On a global scale, we now know that the distribution of species is based upon continental drift.

How are fossils formed?• Preservation in sap • Mineral replacement• Preservation in ice• Traces e.g. footprints• Molds

2. Fossils

I. Fossils

• Fossils are the preserved remains of ancient organisms.

• The succession of fossil forms is congruent with the theory of descent with modification.

• Ex. Extinct intermediate forms in whale evolution.

Ambulocetus natans in action. A reconstruction of an early close cousin of whales.

Other intermediate forms present in the fossil record:

• Why is it true that fossil fishes predate fossil amphibians which predate fossil reptiles which predate fossil mammals?

3. Comparative Anatomy

a. Homologous Structures

b. Vestigial organs

• Vestigial organs are remains of a structure that was functional in some ancestor but is no longer functional in the organism in question.

• For example, humans have a tail bone (the coccyx) but no tail. The presence of vestigial structures is explained by the common descent.

Why does a whale have a pelvic structure?

4. Comparative Embryology:

• A comparison of the early stages of their embryonic development may show similarities that suggest a common ancestry.

• For example, the early embryos of fish, birds, pigs and humans closely resemble one another.

Comparative Embryology

5. Molecular Biology/Biochemical Similarities

• DNA, RNA, amino acids and proteins have all been used to determine evolutionary relationships between organisms

• For example: Cytochrome C (in ETC) is used by organisms ranging from yeast to humans

• The greater the differences in the DNA bases that code for the cytochrome C enzyme, the longer the time since two organisms shared a common ancestor.

• The numbers is equal to the number of amino acid differences between human hemoglobin and others.

An example of molecular homology.

Human beta chain 0

Gorilla 1

Gibbon 2

Rhesus monkey 8

Dog 15

Horse, cow 25

Mouse 27

Gray kangaroo 38

Chicken 45

Frog 67

Lamprey 125

Sea slug (a mollusk) 127

Soybean (leghemoglobin) 124

A phylogenetic "tree of life" constructed by computer analysis of cyochrome c molecules in the organisms shown

Chromosomal Similarities

Examples of Microevolutionch 13 section 7

Why don’t pesticides work very long?

Entomologists say 500 crop pests have already evolved resistance to conventional insecticides.

Insecticide Resistance

• Currently over 500 pests are resistant to 1 or more common insecticides

• Through mutations the insect does not produce enzyme which interacts with the poison

Drug Resistance

• H1N1, MRSA, HIV drug resistance

• Caused by decades of excessive and unnecessary use of antibiotics

In 1943, penicillin was introduced as an antibiotic to protect against Staphylococcus infections.By 1946, a number of strains of Staphylococcus demonstrated resistance to penicillin. Today, as many as 80% of Staphylococcus aureus are resistant to penicillin.

Kettleworth – Biston Betularia

• Prior to the industrial revolution, there was a much higher frequency of the light variety of the peppered moth, which, were adapted to the light colored lichen on tree bark.

• However, industrial pollution in the 1800’s began to kill the lichen, turning the tree bark into a dark color.

• Now, the number of dark variety of peppered moth increased i.e. were naturally selected.

So how fast can you mutate?

• Animals and plants are about 1/100,000 mitotic cells

• Bacteria reproduce by binary fission and mutate about the same….but they multiple every 20 minutes!!!

A single bacteria can reproduce so fast that after 36 hrs, there wouldenough bacteria to cover the Earth 1 foot deep.

Sexual Reproduction

• Genetic variation in sexual reproduction increases

• No way to estimate amount of genetic variation

• Sexual reproduction promotes genetic variation

The genetic structure of a population. Some basic definitions:

• A population is a group of individuals belonging to the same species.

• A species is a group of populations whose individuals can successfully interbreed.

• A gene pool is the total genes in a population a any one time. It consists of all alleles at all gene loci in all individuals of the population.