Class Notes (1,000,000)
CA (620,000)
York (40,000)
BIOL (2,000)
BIOL 1001 (200)
Lecture 1

BIOL 1001 Midterm: [Note] Ernst Mayr's summary of Natural Selection

Course Code
BIOL 1001
Alexander Mills

of 1
Ernst Mayr’s summary of Natural Selection
Observation #1 (Exponential Population Growth Capacity)
oAll species have great potential Fertility
o… therefore, their Population Size would increase Exponentially
o… if All Individuals that are born reproduced successfully
Observation #2 (Stability in Population Sizes)
oPopulation tend to Remain Stable in Size
o… except Seasonal Fluctuations
Observation #3 (Limited Resources)
oEnvironmental Resources are Limited
Inference #1
oProduction of More Individuals than the Environment can support
o… lead to a Struggle for Existence among Individuals of a Population
o… only a Fraction of O/spring would survive each generation
oThere has to be a Struggle among Individuals in a Population (conclusion)
oThe Stability in Population Size is because of a Struggle for Existence due to
Death of those that struggle less well
Observation #4
oIndividuals of a population Vary Extensively in their characteristics
No two individuals are exactly alike
Observation #5
oMuch of this Variation I Heritable
Inference #2
oSurvival in the Struggle for Existence is NOT random
o… BUT depends in part on the Hereditary Constitution of the Individuals
Those individuals whose Inherited Traits best 9t them to their environments
are likely to leave more O/spring than less 9t individuals
Inference #3
oUnequal Ability of Individuals to Survive & Reproduce
o… lead to a Gradual change in a Population
o… with Favorable characteristics accumulating over the generations