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.