Ch13, 36, 37 exam 5 Flashcards
The study of populations
- Populations are studied for the way they change, the way they interact with other populations, and the way they interact with their environments
- In order to understand these interactions scientists must understand the forces that act on populations
POPULATION GROWTH
•ALL POPULATIONS TEND TO INCREASE IN SIZE UNLESS LIMITED BY SOME FACTOR OR FACTORS
GROWTH UNDER THESE CONDITIONS IS CALLED: (population growth)
• EXPONENTIAL
•WHEN THERE IS SOME LIMITING FACTOR THEN POPULATIONS DON’T GROW UNCHECKED AND THERE IS AN EQUILIBRIUM POINT:
•ZERO POPULTAION GROWTH OR THE STATIONARY PHASE
REGULATION OF POPULATION SIZE
•BIOTIC FACTORS : Predation, parasitism, competition : interspecific and intraspecific •ABIOTIC FACTORS : weather •DENSITY-DEPENDENT EFFECTS –Predation –Disease (parasites) –Competition •DENSITY-INDEPENDENT EFFECTS –Usually abiotic : natural disasters –Weather
FACTORS AFFECTING
POPULATION GROWTH
•Density independent: abiotic –Weather –Natural disasters •Density dependent: biotic –Competition •Interspecific : food, shelter •Intraspecific : mating, nesting •Predation •Parasitism
COMMUNITIES
- GROUPS OF POPULATIONS LIVING TOGETHER
- COMPOSITION: NUMBER OF DIFFERENT SPECIES
- DIVERSITY : THE RELATIVE ABUNDANCE OF EACH SPECIES
HABITAT :
–WHERE A SPECIES LIVES (ITS ADDRESS)
•NICHE :
–THE ROLE IT PLAYS IN THE COMMUNITY (ITS JOB)
ECOLOGY
•The study of ecology is in many instances the study of the behavior of groups of living things:
uThe fundamental niche is
the niche of the organism in the absence of competition.
uThe fundamental niche represents
the potential of the organism.
uWith competition, the fundamental niche is not fully realized and the population occupies
its Realized Niche.
uLimiting Factors limit
population growth.
uLimiting Factors may be
resources, or other environmental factors such as temperature or predators.
uLimiting Factors generally are t
hose resources that are scarce relative to their demand.
uWhat is a key limiting factor for most terrestrial (land) organisms?
uWater is a key limiting factor for most terrestrial organisms.
another examples of limiting factors
uPhysical extremes, such as hot or cold temperatures may also serve as limiting factors.
uWhat are limiting factors at the bottom of lakes and the oceans?
sunlight
When does competition occurs
uCompetition occurs between (or among) consumers that share a resource or resources (a resource pool).
uCompetitive exclusion
is the term used when one consumer of a resource pool is so efficient as to exclude other consumers of that resource pool.
The force behind competitive exclusion is
population growth in the face of limited resources
Ecosystem Complexity
- Natural formed ecosystems are very complex
- There are many different organisms all having complex relationships to the other organisms
- When factors change in the ecosystem all of the members are affected.
Evolution is propelled by the following forces:
–Population genetics :changes in genetic make-up of a population
–Natural selection : environmental forces on the gene pool
–Speciation : development of new populations
Fitness:
physical or behavioral characteristics that enable an individual to survive and reproduce.
•Variation :
traits which vary among individuals within a population.
Gene pool :
the total number of alleles available for reproduction within a population.
•Diversity
: the inheritable variations among a population
Adaptation
: characteristic which enables individual to survive and reproduce under specific environmental stresses
Population Genetics
- Studies of the frequencies of a certain allele within a group of individuals (population)
- Predictions about evolution (changes in gene pool) indicated by Hardy-Weinberg Law
Hardy-Weinberg Law
•Describes conditions under which the gene pool will not change : that is no evolution will occur.
–No mutations : no changes in alleles
–Mating is completely random : mating is not based an phenotypes
–No genetic drift : large populations where gene frequencies don’t change
–No gene flow : no alleles leave the population (emigration), no new alleles enter (immigration)
–No natural selection : no environmental forces favor one genotype over another
Natural selection
•Environmental forces upon the gene frequency within a population