Natural Selection Charles Darwin’s “suggestion” about how species change over time.
Evolution refers to changes in a SPECIES, not an individual
4 Key Features to Charles Darwin’s theory of Natural Selection: Variation Competition Fitness Adaptation
Part 1: Variation Individual members of a population have HERITABLE DIFFERENCES: small differences in the base sequence of their DNA The differences that individuals have in their DNA gets passed on to their offspring Happens because of –Random mutations –Sexual reproduction: combinations of gametes
Peppered moths
Part 2: Competition The struggle for survival The amount of resources in a habitat is fixed –Food, water, living space, mates, sunlight, minerals, shelter MANY more individuals are produced during reproduction than will survive There is a limit to how large a population can grow for a given area= carrying capacity
During spring, oak trees have FLOWERS, which produce pollen and egg cells. Pollen will fertilize the egg cells, producing the oak tree seed= the ACORN In one single year, an oak tree may produce up to 2000 acorns. MOST will not grow to be mature oak trees
What eats acorns? Blue jays Pigeons Ducks Mice Squirrels Chipmunks Skunks Raccoons Deer Bears possums Crows Wild pigs Moth larva Weevil larva NOT HORSES: acorns are toxic to them!
Mice A single field mouse can have up to 17 litters of babies each year Each litter can have up to 13 babies That’s 221 baby mice per year from one female MOST get eaten or die: –Hawks, owls, foxes, weasels, snakes
Sunflower One sunflower plant can produce up to 1000 seeds MOST get eaten!!
Part 3: Fitness Genetically, some individuals have traits, either physical or behavioral, that make them better at surviving and reproducing What determines which traits it is good to have??? –THE ENVIRONMENT
Part 4: Adaptation Eventually, as more and more time goes by, and more and more individuals inherit a particular trait, ADAPTATION of the population occurs
Neck stretching
Natural selection?