The Cell’s Blueprint
Cells contain deoxyribonucleic acid (DNA) = heritable material that directs the cell’s activities (metabolism, etc.)
- DNA made up of genes
- Genes are the units of inheritance that transmit information from parents to offspring
- Information is stored in DNA
Evolution
Changes over time
Evolution: diversity and unity
The universal genetic language of DNA unites prokaryotes and eukaryotes.
Natural selection
- differential reproductive success based on adaptation to environment
- descent with modification
- biological fitness = reproduction
Darwin 2 main ideas
- Evolution explains life’s unity and diversity
- Natural selection is the mechanism for evolutionary change, adaptive evolution. Population can change over time if individuals with heritable traits leave more offspring. Results in accumulation of inherited characteristics that increase ability to survive and reproduce.
How does natural selection work?
- Population sizes would increase exponentially, stable in size.
- Environmental resources are limited. Competition for limited resources. Killed by predators, disease, environmental conditions.
- Variations are heritable. Survival depends in part on inherited traits.
- Individuals whose inherited traits give them a high probability of surviving are likely to leave more offspring. Leads to gradual change with favourable characteristics.
Important notes on natural selection
- A population is the smallest group that can evolve.
- A trait that is favourable in one environment may be detrimental in another environment.
- Doesn’t create perfect organisms, allows them to adapt to their environment.
Artificial selection
Humans have modified domesticated plants and animals in just a few generations by selecting individuals with the desired traits for breeding.
Homology : Anatomy
The similarity resulting from common ancestry. Anatomical resemblances that represent variations on a structural theme that was present in a common ancestor.
Homology: Development
Embryonic development of all vertebrates shows remarkable similarities.
Homology: molecular
Genetic code is the same in almost all organisms.
Convergent evolution (analogous)
Characters are similar but are not derived from a common ancestor= analogous. Adapt in similar ways to similar environments.
Steps of natural selection
- Population size increases exponentially then stabilizes
- Environmental resources are limited
- Variations in DNA, heritable traits
- Survival of the fittest, gradual change with favourable characteristics
Aristotle’s view
Viewed species as strict and unchanging
Scala naturale (scale of increasing complexity)
The Old Testament
Species were individually designed by God
Carolus Linnaeus
Founder of taxonomy (grouping similar species into categories)
Attributed similarities to the pattern of their evolution
Fossils
- show that a succession of organisms have populated Earth
Hutton
Proposed a theory of gradualism: change can take place through the cumulative effect of slow but continuous processes
Lyell
Principles of Geology: geologic changes through slow, continuous processes rather than sudden changes
Lamarck
Organisms pass traits to offspring through use and disuse
Unsupported by evidence (DNA)
Where did Darwin get his ideas?
Malthus’ “Struggle for existence “: conflict between population growth and food supply.
Lyell’s principles of geology
Principles of artificial selection
His data ( what he saw in the Galapagos)
