Evolution Flashcards
Voyage of the Beagle
1831 journey on the HMS Beagle by Charles Darwin that led to the proposal of the theory of evolution
Process of proposal to theory of evolution (Darwin’s Journey on the HMS Beagle)
On the Voyage of the Beagle, Darwin collected plants and animals. Observed high levels of diversity amongst organisms. Collected fossils that looked like organisms still alive, but some completely different.
Fixity of Species
Pre-Darwin belief that claimed species do not change, are unrelated, and that Earth is young and has not changed much.
The Galápagos Islands
1000km west of Ecuador. Close together but have different climates. Darwin was especially interested in land turtles and marine iguanas (eg. the shape of a tortoise shell could help identify which island the tortoise belonged to). Darwin wondered if the animals living on different islands had once been the same species, and evolved after becoming isolated from each other.
Fossils (influence on Darwin’s thinking)
Fossils discovered that were much older than what people thought the age of the Earth is.
James Hutton
1795 Geologist who hypothesized that the Earth is very old.
Charles Lyell
1831 Geologist. The processes that shape the Earth now are the same as the processes of the past.
Jean Baptiste Lamarck
Proposed that living things have changed over time, and species are descended from other species. He believed species tend toward perfection and that used functions would become more prominent and vice versa. He also believed in the inheritance of acquired skills.
Thomas Malthus
Noticed that if population growth went unchecked, species would overrun the Earth. Darwin asked what causes the death of many and which factors determine who lives and dies. He concluded that all species tend to produce more offspring than they can support, leading to a struggle for existence
On the Origin of Species by Means of Natural Selection
Book by Darwin published in 1859. Darwin was scared to publish it due to fears of religious backlash
Alfred Russell
Wrote an essay with Darwin summarizing the theory of evolution.
Artificial Selection
Nature provides variations, humans selects traits
Inherited variation
Members of a species vary
Struggle for existence
Members of each species compete for food, space, mates, and other necessities. Predators with high fitness capture more prey, prey with high fitness avoid being caught.
Fitness
An organism’s ability to survive and reproduce in its specific environment. Results from adaptations (inherited characteristics that improve an organism’s chance for survival). Survival of the fittest relates to how low fitness die and are unable to reproduce, while high fitness organisms survive and reproduce.
Types of adaptations
Anatomical (eg. quills on porcupine), Physiological (eg. photosynthesis), Behavioral (live/hunt in groups).
Natural Selection
Results from no human intervention and results in higher fitness amongst populations.
Descent with Modification
Over large amounts of time, natural selection produces organisms with different structures, niches, and habitats and look different from their ancestors. Ie. each living thing has descended with changes, from other species over time.
Evidence that living things have been evolving on Earth for millions of years (3 pieces of evidence)
Fossil record
Geographic distribution of living species
Homologous body structures (body part with the same basic structure as that of another organism but not the same function)
Embryology
Smilitaries in early development. Also evidence that living things have been evolving.
Darwin’s conclusion based on fossil records
Organisms had come into being, lived, and vanished. Ie. Life had changed over time
Convergent Evolution
Organisms develop similar features and behaviors due to similar environment
Analogous Structrues
Same function, different structure (eg. bat wing vs butterfly wing)
Divergent Evolution
Species becoming more distinct due to environmental differences.
Homologous Structures
Same structure, different function. Are constructed from the same basic bones. They can also be structures that have different mature forms but develop from the same embryonic tissues.
Vestigial Organs
Organs that serve no useful function in an organism, but is not eliminated by natural selection as it does not effect the organism negatively.
Role of DNA on evolution
Mutations control evolution
Variation in species
Random mixing of genes from parents during meiosis
Single gene trait
Trait controlled by one allele
Polygenic trait
Trait controlled by many alleles
Relative frequency
How often an allele is seen in the gene pool. A change in relative frequency is evolution.
Directional Selection
One end of the curve has higher fitness (eg. bird beaks become larger and larger)
Stabilizing Selection
Middle of curve has higher fitness (eg. babies born at average mass are more likely to survive)
Disruptive Selection
Both ends of curve have higher fitness (eg. larger and smaller seeds become more common).
Speciation
The formation of a new species. Population must be divided
Reproductive Isolation
Members of two populations are unable to interbreed
Causes of Reproductive Isolation
Geographic Isolation, Behavioral Isolation, Temporal Isolation
Natural Selection Effect on Polygenic Traits
Distributions of phenotypes can be affected through: Directional Selection, Stabilizing Selection, Disruptive Selection
Geographic Isolation
Two populations separated via geographic barriers
Behavioral Isolation
Capable of interbreeding, but have different reproductive behaviors that prevent interbreeding
Temporal Isolation
Species reproduce at different times
