Chapter Four: Evolution Flashcards
Evolution
The gradual development of organisms over time.
Common Descent (3)
- All organisms are composed of cells
- All take in chemicals and energy from the environment
- All reproduce, respond to stimuli, and evolve
Fossil
The preservation of the general shape of an organism. Formed when minerals in the earth harden over it’s body upon its death
Transition Fossil
A fossil representing an evolutionary link in the fossil record, indicating a common ancestor
Strata
Layers of the earth representing geological periods of time.
Relative Dating
- Fossil dating method using layers of strata to determine which era it came from. The lower the strata, the older the fossil
- Only accurate if the strata has not been twisted or upturned from natural processes
Radiometric/Absolute Dating
Dating method which uses the half-lives of isotopes present in the fossil to determine its age. In organic fossils, carbon is typically used.
Mass Extinction
Event that extinguishes a large number of organisms in a short period of time. This causes only the most well-adapted organisms to survive.
What is an example of a mass extinction?
The Cretaceous period; a large number of meteorites hit the earth and the debris blocked the sunlight. Many plants and animals died.
Biogeographical Evidence for Evolution
- Study of the distribution of plants and animals
- continental drift shown through distribution of similar fossils on different continents: evolving species unable to migrate
Homologous Structure ( + example)
Has same function and basic structure, indicates a common ancestor
ex) A human arm and a whale forelimb
Analogous Structure ( + example)
Same basic function but different origin
ex) bird’s wing and bee wing
Vestigial Structure ( + example)
Anatomical structure fully functional in one group and reduced or nonfunctional in another
ex) Human coccyx (tailbone)
Biochemical Evidence for Evolution
- All organisms have the same three basic biochemical molecules: DNA, ATP, and general enzymes
- The degree of similarity between DNA base sequences and amino acid sequences indicate the degree of relatedness
Evolution of micromolecules
Earth’s early atmosphere according to Miller was full of methane, hydrogen, and ammonia
-when applied with enough each (ex lightning) these molecules could form organic compounds and amino acids
Miller Experiment
Simulated conditions of early earth (methane, hydrogen, and ammonia) and applied an electric spark. Yielded amino acids without the use of oxygen.
Macromolecules: RNA first hypothesis
RNA functioned both as an enzyme and a substrate. Some viruses use RNA as their genetic material
Macromolecules: Protein first hypothesis
Sidney Fox’s experiments
- amino acids can form polypeptides when exposed to dry heat
- amino acids collected in puddles and formed proteinoids within microspheres
Microsphere
A chemical reaction separated from its environment
Macromolecules: Cairnes-Smith hypothesis
- Proteins and RNA at the same time: Clay attracted small organic molecules, which served as inorganic catalysts for polypeptide formation
- Fueled by energy from radioactive decay
The Protocell
- Proposed structure of a protein-lipid membrane which carried on an energy metabolism
- Microspheres were exposed to lipids, created a coacervate with a protein-lipid membrane
- the phospholipid automatically formed a liposome
Coacervate
Microscopic spontaneously formed spherical collection of lipid molecules, held together by electrostatic forces
Liposome
A spherical structure with at least one lipid bilayer
The Heterotroph Hypothesis
- Since nutrition was plentiful in the ocean, the first organism was probably a heterotroph
- used ATP first; was a fermentative process
- Had a catalytic ability like microspheres and took in available enzymes (beginning of glycolysis)
The True Cell (RNA first hypothesis)
-First true cell had RNA genes; reverse transcriptase produced DNA from RNA
Reverse Transcriptase
An enzyme that generates complimentary DNA from an RNA template. Requires DNA polymerase and a nucleus
The True Cell (Protein-first hypothesis)
Complex enzymatic processes may have been necessary for the formation of DNA and RNA - requires proteins
The True Cell (Cairnes-Smith hypothesis)
RNA genes could replicate because proteins present for catalysm. Once protocells could replicate, they became true cells
Order of the Evolution of the Cell (5)
- Micromolecules
- Macromolecules
- The Protocell
- The Heterotroph
- The True Cell
Microevolution
A change in the gene frequency of a population
Population
All members of a species occupying a particular area
Hardy-Weinberg Law
Equilibrium of allele frequencies in a gene pool will remain constant in each generation of a large sexually reproducing population, as long as certain conditions are met.
Hardy-Weinberg Equation
p2 + 2pq + q2
Agent of Evolutionary Change: Mutations
Only source of new alleles in a population; can also be an adaptive variation.
Gene Pool
the sum total of all alleles in a population
Agent of Evolutionary Change: Genetic Drift
Change in allele frequency due to chance
Founder Effect
A few individuals found a colony and their collective genes represent a small fraction of the original gene pool
Bottleneck Effect
Population is subjected to near extinction by a disaster and only a few genotypes contribute to the next generation
Agent of Evolutionary Change: Gene Flow
Movement of alleles between populations, keeps the gene pools of two or more populations similar
Agent of Evolutionary Change: Nonrandom Mating
Individuals pair up according to genotype and phenotype. Increases frequency of recessive abnormalities (ex. inbreeding)
Agent of Evolutionary Change: Natural Selection
Process by which populations adapt to their environment.
Requirements for Natural Selection (4)
- Variation
- Inheritance
- Differential Adaptiveness (some differences have a survival benefit)
- Differential Reproduction (better adapted individuals survive to reproduce more offspring)
Fitness
Measured by the number of fertile offspring produced by an individual. Variations occur from mutations, crossing over, and independent assortment.
Stabilizing Selection
An intermediate, or average, phenotype is favoured. Improves adaption of a population to a stable environment.
Directional Selection
An extreme phenotype is favoured. Distribution curve shifts in that direction.
Species
A group of interbreeding sub populations that share a gene pool
Premating Isolation Mechanisms (4)
Reproduction never attempted
- Habitat Isolation
- Temporal Isolation
- Behavioral Isolation
- Mechanical Isolation
Premating Isolation Mechanism: Habitat Isolation
Species at same locale occupy different habitats
Premating Isolation Mechanism: Temporal Isolation
Species reproduce at different seasons or different times of day
Premating Isolation Mechanism: Behavioral Isolation
Courtship behaviour differs; species respond to different songs, calls, pheromones, or other signals
Premating Isolation Mechanism: Mechanical Isolation
Genitalia unsuitable for one another
Postmating Isolation Mechanisms (4)
Reproduction may take place but it does not produce fertile offspring
- Gamete Isolation
- Zygote Mortality
- Hybrid Sterility
- F2 Fitness
Postmating Isolation Mechanism: Gamete Isolation
Sperm cannot reach or fertilize egg
Postmating Isolation Mechanism: Zygote Mortality
Fertilization occurs, but zygote dies
Postmating Isolation Mechanism: Hybrid Sterility
Hybrid survives but is sterile and cannot reproduce
Postmating Isolation Mechanism: F2 Fitness
Hybrid is fertile, but F2 has reduced fitness
Allopatric Speciation
Geographical barriers separate a population into two groups
Sympatric Speciation
Separation occurs without any geographical barriers. Two subgroups of a population becomes reproductively isolated.
Phyletic Gradualism
Change of species is slow but steady after a divergence
Punctuated Equilibrium
Stasis is punctuated by speciation, occurs too rapidly to fossilize
Cladogram
A branching, tree-like diagram with successive points of divergence from a common ancestor
Cladistic
A branch of a cladogram
Clad
The specific trait of analyzed in a cladogram
