3 Mechanisms and Evidences of Evolution Flashcards
- process that changes the genes of populations of organisms over time
Evolution
Evolution may be used to explain:
- origin of species
- diversity of organisms and their relationships
- similarities and differences among species
- adaptations to the environment
one of the alternative forms of the same genes
Alleles
– a group of individuals of a single species
inhabiting a certain area
Population
- evolutionary process that changes
anatomy, physiology or behavior, resulting in an
increased ability to live in a particular environment,
happens in a POPULATION (not individual)
Adaptation
- proposed by a Greek philosopher that life arose in water.
- simpler forms of life preceded complex form.
Anaximander
- French naturalist who predicted that the Earth is <6000 years old and suggested that different species may have arisen from common ancestors, though he later argued against it.
- known to be the father of Biogeography
Georges-Louis Leclerc, Comte de Buffon
- French naturalist who proposed the inheritance of acquired characteristics.
- though erroneous, his idea provided
strong advocacy for the concept of
evolution
Jean Baptiste Lamarck
Lamarck’s inheritance of acquired characteristics is also known as…
Use and Disuse Theory
- British naturalist who propose together with Alfred Wallace the evolution by natural selection.
- Wrote On the Origin of the Species by
Means of Natural Selection
Charles Darwin
- Organisms beget like organisms
- There are chance variations between individuals in a
species. Some variations are heritable. - More offspring are produced each generation that can
be supported by the environment. - Some individuals, because of their physical or
behavioural traits, have a higher chance of surviving and
reproducing.
Theory of Natural Selection
- An Austrian monk that laid down the foundations of heredity.
- Showed that traits can be inherited in a well-defined and predictable manner.
- Darwin could not explain how his traits that lend fitness can be inherited.
Gregor Mendel
Laws of Inheritance:
- For each trait, there are two alleles that are
separated during gamete formation, to be joined
randomly during fertilization.
Law of Segregation
Laws of Inheritance:
- Different genes from different traits are passed
independently from parent to offspring.
Law of Independent Assortment
- Japanese biologist who proposed the neutral theory of evolution.
- The molecular changes represented by majority of molecular differences do not influence the fitness of the individual organism.
Motoo Kimura
This theory exempliied by the DEGENERACY of the genetic code.
Neutral Theory
Who Elucidated the structure of DNA based on X-ray crystallography data of Rosalind Franklin?
American molecular biologist James Watson and British
physicist Francis Crick
He identified DNA as the genetic material.
Oswald Avery
Result of differences in survival and reproduction
among phenotypes.
Natural Selection
Key challenges to living organisms
- Find appropriate habitat and environmental conditions
- Obtain necessary resources
- Avoid predators
- Find a mate (or mates)
- Produce as many successful offspring as possible
Exchange of genes between populations, mostly of the
same species, and regulated by migrations
Gene Flow
Change in gene frequencies in a population due to
chance or random events
Genetic Drift (eg. Bottleneck effect, founder effect)
Microevolution - _______
Macroevolution - ________
- below the species level.
- at or above the species level.
- Plant and animal breeding -> led to the emergence of various crop plants and different breeds of farm animals.
Artificial Selection
- e.g. sickle-cell anemia
- ss – people with misshapen red blood cells
- Ss – people that are less susceptible to
malaria - Presence of malaria in Africa acts as a
selection pressure to maintain the recessive
allele in the population - e.g. British peppered moth Biston
belutaria - During the Industrial Revolution,
white moths were nearly
decimated, either because they
were more susceptible to air
pollution or they were more
conspicuous to bird predators
Genetic variation maintained by
natural selection
- e.g. Archaeopteryx
- Discovered by Von Mayer in Germany
- Missing link between reptiles and birds
e.g. Tiktaalik roseae
* Discovered by Edward B. Daeschler in Canada
* Missing link between non-tetrapod fishes and tetrapod amphibians
Fossil Record
- Presence of HOMOLOGOUS STRUCTURES or structures with the same embryonic origin
- Homologous structures must be distinguished from ANALOGOUS STRUCTURES or structures that resemble
each other physically or functionally but do not have the same embryonic origin
Comparative Anatomy
- Closely related organisms have similar stages in their embryonic development
Comparative Embryology
Embryonic development in vertebrates
- possess a dorsal, hollow nerve cord
- a notochord (stiffening rod of
cartilage) in the back - similar membranes in the embryos
- yolk sac that produces the first blood
cells and germ cells - similar development of many organs
- Related individuals have greater similarity in their DNA and proteins than do unrelated individuals
Molecular Biology
Patterns of Macroevolution:
- When two or more biological characteristics have a common evolutionary origin but have diverged over evolutionary time
- Also known as ADAPTIVE EVOLUTION
Divergent Evolution
Patterns of Macroevolution:
- Organisms not closely
related that
independently evolve
similar traits as a result
of having to adapt to
similar environments or
ecological niches - Exemplified by
analogous structures
Convergent Evolution
Patterns of Macroevolution:
- The independent evolution
of similar traits, starting from
a similar ancestral condition - NOTE: When both
descendants are similar in a
particular respect, evolution is
defined as parallel if the
ancestors considered were
also similar, and convergent
if they were not.
Parallel Evolution
Types of Speciation:
- a physical barrier divides a population
- the isolated populations then undergo genotypic and/or phenotypic divergence as they (a) become subjected to dissimilar selective pressures or (b) they independently undergo genetic drift
Allopatric speciation
Types of Speciation:
- Small founding population enters isolated niche
- New species are formed in isolated, small peripheral populations
which are prevented from exchanging genes with the main
population
Peripatric speciation
Types of Speciation:
- New niche found adjacent to original one
- There is no specific extrinsic barrier to gene flow. The population is
continuous, but nonetheless, the population does not mate randomly.
Individuals are more likely to mate with their geographic neighbors
than with individuals in a different part of the population’s range
Parapatric speciation
Types of Speciation:
- Speciation occurs without physical separation
- Can be attributed to dependence on different hosts (e.g. plants) or
increase in chromosome number through polyploidy
Sympatric speciation
