Evolution- change overtime
Evolution by means of natural selection is the process by which genetic mutations that enhance reproduction that become and remain more common in successive generations of a population.
Lamarck: (19th Century) inheritance of acquired characteristics and use and disuse... individual organisms change in response to their environment
Darwin: (1859 On the Origin of Species) natural selection, those who are better fit to survive will and pass on their traits to their offsping (survival of the fittest) |
5 conditions that will exist to prevent evolution, keeping phenotypes and allelic frequencies constant
1. Large populations
2. Isolated populations (no immigration or emigration)
3. No Mutations
4. Random Mating
5. Random reproductive success
2. Isolated populations (no immigration or emigration)
3. No Mutations
4. Random Mating
5. Random reproductive success
Genetic mutations are what will cause an increase in a gene pool of a population, and it may eventually allow for evolution
A new flu vaccine is needed every year since the influenza virus evolves so rapidly
An entire population of bacterium may "become" resistant to a particular antibiotic in a matter of months... individual bacteria to not evolve, it is the population that evolves.
Treatment for AIDS (acquired immune deficiency disease) is a cocktail of drugs called AZT, which can slow the progression of the disease
The virus that causes AIDS becomes resistant to these drugs because the virus can mutate and evolve rapidly.
Those that are susceptible to the drugs become inactivated, while those that have mutated are resistant.
A new flu vaccine is needed every year since the influenza virus evolves so rapidly
An entire population of bacterium may "become" resistant to a particular antibiotic in a matter of months... individual bacteria to not evolve, it is the population that evolves.
Treatment for AIDS (acquired immune deficiency disease) is a cocktail of drugs called AZT, which can slow the progression of the disease
The virus that causes AIDS becomes resistant to these drugs because the virus can mutate and evolve rapidly.
Those that are susceptible to the drugs become inactivated, while those that have mutated are resistant.
Important Concepts of Evolution
- Evolution is not always a slow process
- Evolution does not occur at the same rate in all organisms
- Evolution does not always cause organisms to become more complex
- Evolution occurs in populations, not individuals
- Evolution is directed by changes in the environment
Evidence for Evolution
1. Fossil Record
2. Comparative anatomy
3. Comparative biochemistry
5. Molecular biology
6. Biogeography
- 99% of all organisms that ever lived on Earth are now extinct
- Earth ~ 4.6 billion years old
- Prokarytotic cells are oldest fossils to live on Earth
- transitional fossils LINK older extinct fossils to modern fossils
- EX: Eohippus the ancient horse is an ancestor of the modern horse, Equus
2. Comparative anatomy
- homologous structures: wing of bat, fin of whale, human arm shows common bone structure (despite various functions of the limb)
- We diverged from a common ancestor millions of years ago. (divergent evolution)
- analogous structures: bat wing and fly's wing (same function, different structures... superficial and reflects adaptions to a similar environment, NOT Evidence of a common ancestry)
- vestigial structures: anatomy of animals has evolved... certain structures were once needed but no longer needed (Ex: appendix)
3. Comparative biochemistry
- similar DNA and proteins are found in organisms that share a common ancestor
- EX: humans and mice are both mammals, they share many common proteins/DNA. This relationship is why we test new medicines on mice and extrapolate the results to humans
- closely related organisms have a common development as an embryo
- EX: all vertebrates embryos go through a stage in which they have gill pouches on the sides of their throat.... in fish, gill pouches -> gills, in humans, gill pouches -> eustachian tubes of the middle ear and throat
5. Molecular biology
- all aerobic organisms contain cells that carry out respiration that requires the ETC, and certain polypeptides (enzymes)
6. Biogeography
- theory of continental drift = the continents were locked together in the supercontinent of Pangea ~ 250 million years ago.
- location of fossils confirms that marsupials migrated by land from South America to Antarctica to Australia before the continents separated... Today, most of the worlds marsupials are isolated in Australia. (marsupial : mammals that are born incompletely developed and are carried in the mother's belly until development completes)
Representation of Evolution- Phylogenetic Trees and Cladograms
Classification:
Organisms are classified into categories based on similaritiest based on evolutionary history anatomical structures, and reproductive and development.
The following categories are provided, from the broadest and most inclusive groupings to the most specific and least inclusive groupings..
Organisms are classified into categories based on similaritiest based on evolutionary history anatomical structures, and reproductive and development.
The following categories are provided, from the broadest and most inclusive groupings to the most specific and least inclusive groupings..
- Kingdom
Phylum
Class
Order
Family
Genus
Species
The last two 'categories' are the way we name an organism- Genus species (Ex: Homo sapien- the scientific name for a human).
Dichotomous keys help scientists determine the Genus and species of an unknown organism by inspected the presence or absence of certain features.
See the following image:
See the following image: