How Populations Evolve Flashcards
Theory of Evolution
- Inspired by 5 year voyage
- The idea that Earth’s species are descendants of ancestral species different than those living today
Early views on evolution
- Some early Greek philosophers suggested that life might change gradually
- Aristotle and Judeo-Christians believed that species are perfect and unchanging
Fossils
- The imprints or remains of organisms that lived in the past
- In the century prior to Darwin, fossils had been collected which suggested change over time
Lamarck’s Theory
- Jean-Baptiste Lamarck suggested that organisms evolve by the use of disuse of body parts
- Acquired characteristics are passed to offspring
Lyell’s Principles of Geology
- Inspired Darwin
- Suggested that natural forces gradually changed the earth and these changes are still happening today
Geology & Paleontology
- Darwin learned from geology that the earth was very old
- He learned from paleontology that over time, species had changed due to natural processes
On the Orgin of Species
- Darwin’s book, stated that:
- Evolution is done through natural selection
- As organisms spread, they acquire diverse adaptations specific to their environments
Artificial selection
- When humans modify a species through selection and breeding
- Also known as selective breeding
- Established by Robert Blackwell during the British Agricultural Revolution
Over Population
- A connection between natural selection and the ability to over-reproduce
Thomas Malthus
-Malthus argued that human suffering was due to the human population expanding faster than it’s resources
Darwin & Over Population
- Darwin concluded that
- Organisms vary in traits and produce more offspring than the environment can handle
- Organisms with better traits leave more offspring
- The unequal reproduction will lead to an accumulation of favorable traits
Evolution’s 5 Key Ponts
- Individuals don’t evolve, populations do
- Natural selection can increse or decrease any heritable traits
- Acquired trait’s can’t be passed on
- Evolution doesn’t lead to perfection
- Favorable traits vary with environtment changes
Darwin’s Finches
- Studied by Rosemary & Peter Grant for over 30 years in the Galapagos
- In wet years, small seeds are abundant and small beaks are favorable
- In dry years, largebeaks are favorable because small seeds are in low supply
Pesticide Resistance
- A small amount of new pesticides may kill 99% of pests, but subsequent spraying’s will be less effective
- Surviving insects have alleles to resist pesticides
- Therefore, the population gets more resistent over time
Key points of natural selection
- Natural selection is an editing process, not a march to perfection
- Natural selection is contingent on time and place, favoring those characteristics that fit the current environment
Fossil Record
-The sequence in which fossils appear within the strata of sedimentary rocks
Historical sequences
- Speicies have evolved in historical sequences
- The oldest known fossils go back 3.5 bil years ao and are prokaryotes
- The oldest eukaryotic fossils are a billion years younger
Fossil Links
- Fossils often link early, extinct species to living species
- A series of fossils traces the gradual modification of jaws and teeth in mammals
- A series of fossils shows whales coming from land mammals
Biogeography
- The geographic distribution of a species
- Suggests that organisms evolve from common ancestors
- Daein noted Galapogos animals look more like s. american animals than animals from other islands
