Traits or structures that were needed in ancestral functions but no longer needed in the current animal.
-Insects with wings that can't fly
1. The ability of a population to expand is infinite, but the ability of the environment to support populations is always finite.
2. Organisms within populations vary, and this variation affects ability of organisms to survive and reproduce.
3. Variations are transmitted from parents to offspring
Postulate 1: Birds in the Galapagos
-Environment constrains population growth
-Severe drought occurred 1976-78
• Drought affected seed availability
• Many birds died of starvation
Postulate 2: Birds in the Galapagos
-individuals vary in the ability to survive and reproduce
• Beak size varies
• Small beaked birds have trouble with large seeds
• During drought, larger beaked birds were at advantage
Postulate 3: Birds in the Galapagos
-Variation is transmitted from parents to offspring
• Beak size is inherited
The evolution of Peppered moth
-Originally, the vast majority of peppered moths had light colouration, which effectively camouflaged them against the light-coloured trees and lichens which they rested upon.
-Coal buring during the Industrial Revolution in England, many of the lichens died out, and the trees that peppered moths rested on became blackened, causing most of the light-coloured moths, or typical, to die off from predation.
-At the same time, the dark-coloured, moths flourished because of their ability to hide on the darkened trees
-adaptation arose by chance and spread by natural selection
Darwin defined evolution as
Descent with modification
Fitness is context specific
1. in comparison to others in group
2. at a specific place and time
3. sometimes at the expense of others
How do random processes generate complex adaptations?
1. Cumulative retention of small changes
2. Each changes increases fitness, giving individuals within populations small advantages over their competitors
1. Unsure if blending inheritance was the mode by which traits were passed on through generations
2. Heritability of instincts
How is variation maintained?
1. Mendelian genetics is a partial explanation
2. Variation hidden in recessive alleles
Genotype vs phenotype
-Genotype: organism's set of genes
-Phenotype: organism's physical characteristics
Where do novel traits come from and how do species move beyond the apparent range of variation in the population?
•Mendelian genetics is a partial explanation - Variation “hidden” in recessive alleles (Blending inheritance is not true)
•Recombination is a partial explanation
•the implications of multiple loci contributing to a trait
Why does natural selection act on the phenotype rather then the genotype?
Because the phenotype or physical characteristics is what actually determines if the organism is able to reproduce and pass along its genotype to the next generation
-is a theory that states that the individuals that are best adapted to their environment will survive and reproduce most successfully. -Natural selection acts on physical traits and not on an individual's genes.
-The measure of an individual's ability to survive and reproduce is called
-The more advantageous traits an individual has, the more fit the individual is