Chapter 1 Flashcards
Adaptation
A feature of an organism created by the process of natural selection
Results from the competition of individuals, not between entire populations or species.
Natural selection
The process that produces adaptation.
Based on Three Postulates:
1. The availability of resources is limited
2. Organisms vary in the ability to survive and reproduce
3. Traits that influence survival and reproduction are transmitted from the parents
When these three postulates hold, natural selection occurs
Three Postulates of Natural Selection
- The availability of resources is limited
- Organisms vary in the ability to survive and reproduce
- Traits that influence survival and reproduction are transmitted from the parents
When all three occur, natural selection occurs.
Morphology
The form and structure of an organism.
Also a field of study that focuses on the form and structure of an organism.
Equilibrium
Of a population: a steady state in which the composition of the population does not change
Produced by stabilizing selection
Stabilizing selection
Selection pressures that favour average phenotypes.
Stabilizing selection reduces the amount of variation in a population but does not alter the mean value of a trait.
Stabilization selection produces equilibrium state.
Trait
A characteristic of an organism created
Character
A trait or attribute of the phenotype of an organism
Species
A group of organisms classified together at the lowered level of the taxonomic hierarchy
** Biologists disagree about how to define a species *
Stasis
A period or state of stability burning which little or no evolutionary change in a lineage occurs
Fecundity
The term demographers use for the ability to produce offspring
In humans, fecundity may be greater than fertility (the actual number of children produced) when people limit family size.
Low fecundity females = produce only 2 offspring a year - the offspring spring will then be low fecundity daughters.
High fecundity females = produce 10 offspring a year - the offspring spring will then be high fecundity daughters.
This will result in a higher proportion of high fecundity offspring compared to low fecundity. High fecundity offspring will increase rapidly due to there being more producing each population versus the low fecundity. - the more population of the rapidly increasing species, the higher the chance of extinction due to depletion of resources.
Continuous variation
Phenotypic variation in which there is a continuum of types
Ex. Height in humans
Humans grade smoothly from one extreme to another (short to tall) , with intermediate types (heights between)
Discontinuous Variation
Phenotypic variation in which there is a discrete number of phenotypes with no intermediate types.
Usually quite rare in nature.
Ex. Pea colour in Mendels experiments. Or drawfism in human height.
Not important to evolution of complex adaptations because they are extremely unlikely to arise in a single jump.
Convergence
The evolution of similar adaptation in unrelated species or distantly related populations of the same species.
Ex. The evolution of the camera type eyes in both vertebrates and mollusks
Placental mammals
A mammal that gives birth to live young that developed in the uterus and were nourished by blood delivered by placenta
Marsupials
A mammal that gives birth to live young that continue their development in a pouch equipped with mammary glands
Ex. Kangaroos, opossums
Blending inheritance
A model of inheritance that assumes the mother and father each contribute a hereditary substance that mixes or blends to determine the characteristics of the offspring
widely accepted during the 19th century
Believed by Darwin and many people
