QUIZ APES POPULATIONS
Population Distribution + Stats
3 TYPES:
Uniform
Caused from competition
Random
Rare
Truly random distribution means that the individuals have little to no interaction & resources are readily available
Clumped
Most Common Due to resources
Population Equations:
Pop change: (births + immigration) - (deaths + emigration)
The growth rate: (Change in population/ Population size) * 100%
Growth Rate:
To calculate from starting size to new size:
Use % Change
New - Old/ Old * 100%
To calculate from births, deaths, etc.
Use (B+I) = (D+E) or Original size * 100%
To calculate from percent births, deaths, etc
Use %B - %D = Growth rate%
To calculate from crude birth, crude death, etc.
Use CBR-CDR/10 = growth rate %
Population size is affected by density-dependent & density independent factors:
Density dependent: A factor that influences an individual’s probability of survival and reproduction in a manner that depends on the size of the population
Density-independent: A factor that has the same effect on an individual’s probability of survival and the amount of reproduction at any population size.
Exponential Growth:
Biotic potential: maximum reproductive rate of a population in ideal conditions
J SHAPED CURVE
Abiotic Contributing Factors:
Favorable light
Favorable Temperatures
Favorable chemical equipment - nutrients
Biotic Contributing Factors:
High productive rate
Generalized Niche
Ability to migrate/disperse ability
Defense mechanisms
Can cope with adverse conditions
Exponential growth equation & practice:
Logistic Growth:
Enviromental resistance: all the factors that act to limit the growth of a population
Results in an S curve once carrying capacity is reached
Populations that grow too fast may experience an overshoot and die-off
Abiotic Contributing Factors:
Unfavorable Light, temps, and chemical enviroment - nutrients
Biotic Contributing Factors:
Low Reproductuive Rate
Specialized niche
Inability to migrate or disperse
Inadequate defense mechanisms
Inability to cope with adverse conditions
Carrying capacity:
Population at which growth = 0
Population can overshoot and die off, but will eventually reach the carrying capacity of the ecosystem
Isle Royale Case Study:
Top down population control: when predators keep a population from growing as large as it could
Bottom-up population control
When food availability keeps a population from growing as large as it could.
Succession Island Biogeography
Theory of Island Biogeography:
Theory of island biogeography - the theory that explains that both habitat size and distance determine species richness
Applies to oceanic islands and habitat islands like national parks
The influence of habitat size and distance:
Larger habitats have more species
Succession:
Succession is a series of changes that occur as an ecosystem develops
Initial species are called pioneer species — they set the stage for the appearance of other species of other species eventually resulting in a climax community.
Primary:
Succession that occurs on newly formed soil
Ex; Volcanic flows, glacier movement, etc
Secondary
Succession that occurs post an ecological disruption
Ex: post mining, post fire, post flood
Metapopulations:
• A “population of populations”
– Occasional immigrants from larger nearby populations can add to the size of a small population an
introduce new genetic diversity
– The number of species that exist as metapopulations is growing because human activities have fragmented habitats, dividing single large populations into several smaller populations.
– Identifying and managing metapopulations is thus an increasingly important part of protecting biodiversity
Several local populations linked by regular or occasional gene flow
Example: Bay checkerspot butterfly in California exists in several habitat patches, moving occasionally between them
Vital role in conservation, especially when fragmentaed
Reproductive Strategies, Survivorship Curves
Reproductive Strategies:
Goal of each species is to produce as many viable offspring as possible
Each individual has a limited mount of energy to put towards life and reproduction
This Leads to a trade-off of long life or high reproductive rate
Natural Selection has lead to two strategies for species: r-strategists and K- strategists
K-strategists:
Focus on a long life
Elephants, humans, and redwoods
Have few off spring and take care of them for a long time
Long period of time between birth & reproduction
R-strategists:
Focus on reproduction
Insects, bacteria, mice, rabbits
Have lots of offspring, but most will not survive adulthood
Short period between birth and reproduction
Survivorship Curves:
I. Late Loss: K-strategies -
few young
care for young until reproductive age
low juvenile mortality
Ii. Constant Loss:
Intermediate reproductive strategies with constant mortality (birds)
Iii. Early Loss: R- strategists
Many offspring
High infant mortality
High survivorship once a certain size/age
Speciation:
Partial niche overlap
Both compete in the overlapping parts of the niche
If the overlap is minimal, both species can coexist by specializing
Called resource partitioning
Full niche overlap
both compete directly for the same resources
One specie will be more suited and out-compete the other specie
Called the Competitive Exclusion Principle.
Species Interactions:
Mutualism: ecological interaction where both organisms benefit
Predation: ecological interaction where one organism eats another, prey
Commensalism: ecological interaction where one organism benefits while the other isn’t unaffected
Parasitism: a parasite where they live on another organism, causing them harm.
Keystone species:
essential to maintain ecosystems
Control population of another species or by altering/creating the habitat for other species
Sea Otters & Elephants