Population changes
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Population Changes. Distribution Patterns are Fluid. Distribution Patterns are Fluid. For each population, the distribution pattern is a product of complex interactions between behaviours and other characteristics that increase each individuals chances of reproduction and survival.

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Population changes

Population Changes

Distribution Patterns are Fluid

Distribution patterns are fluid
Distribution Patterns are Fluid

  • For each population, the distribution pattern is a product of complex interactions between behaviours and other characteristics that increase each individuals chances of reproduction and survival

  • http://www.appinsys.com/globalwarming/GW_4CE_Animals.htm



Review of Distributionhttp://roadtravelafrica.com/2010/11/26/meerkats/ http://blog.webosaurs.com/2011/02/09/wolverines-disappearing-from-the-us/

Ex. #2 Wolverines – territorial in an area with evenly

distributed food

Ex. #3 Tropical Fig – seeds

are randomly distributed

in tropical rain forests

** this type of distribution is

very rare

Ex. #1 Meerkats – live in groups gathered near resources

Immigration emigration natality mortality n b i d e
Immigration, Emigration, Natality & Mortality ΔN = [B+I]- [D+E]

How Populations Change Size

Immigration vs emigration
Immigration vs Emigration



The movement of individuals out of a population

  • The movement of individuals into a population

  • For most species immigration/emigration has little impact on population size

  • Exception include human populations (we move more than is typical for a species) and invasive species such as zebra mussels

  • Open populations have immigration/emigration,

  • closed populations do not!

  • http://www.cloca.com/lwc/streams_invasive.php

  • http://www.awdalpress.com/index/?attachment_id=15131

Natality vs mortality
Natalityvs Mortality





  • Birth

  • http://favim.com/image/68983/

  • As the population density increases, birth rates often decrease and death rates typically increase

  • Since most populations are not greatly effected by immigration/emigration:

  • ΔN = B-D EX. In a population of slow loris, 24 were born

  • Δ → change and3 died the population size is:

  • N → population size

  • B → births ΔN = B-D ΔN = 24 - 3

  • D → Deaths ΔN = 21

Aspects of natality
Aspects of Natality

Fecundity, Survivorship, r- and k- selected strategies


  • The average number of offspring produced by a female over her lifetime

  • This tends to be inversely related to the amount of care a parent provides

  • Ex. Turtles have a high fecundity, while gorilla’s have low fecundity




  • The number or percentage of organisms that typically live to a certain age in a given population

  • Type I shows a high rate of rate of juvenile survival and individuals that live to sexual maturity and beyond EX. Humans

  • Type II shows a constant risk of mortality throughout an individuals lifetime EX. squirrels

  • Type III most individuals die as juveniles, only a few live long enough to produce offspring, and fewer live to old age EX. oysters

  • http://mycozynook.com/102RGCh36OH.htm

R and k selected strategies
r- and k- selected Strategies

r- selected strategy

K- selected strategy

Live a relatively long life span

Become sexually mature later in life

Produce few offspring per reproductive cycle

Provide a high level of parental care

  • Short life span

  • Become sexually mature at a young age

  • Produce large broods of offspring

  • Provide little or no parental care to their offspring

  • Most populations fall somewhere between these two strategies

  • Describing if a population is r-selected or k-selected requires that it be compared to another population

Population growth models
Population Growth Models

Unlimited and Limited Environments

Biotic potential
Biotic Potential

  • The highest possible per capita growth rate for a population

  • AKA intrinsic rate of natural increase (r)

  • A species’ biotic potential is related to its fecundity

  • http://www.underwater.org/mermaid/tanzania/underwater3.html

Unlimited environment
Unlimited Environment

Exponential Growth Model

Geometric Growth Model

Deaths can occur throughout the year, but births are restricted to a breeding season

Sampling occurs on a yearly (usually) basis

  • Births and deaths can occur throughout the year, (no fixed breeding season)

  • Sampling can be continuous

EX. Humans

EX. Sparrows

J shaped growth curve
J-shaped Growth Curve

  • This graph traditionally represents exponential growth

  • At the bottom there is a lag phase followed by an exponential growth phase

Limited environments carrying capacity
Limited Environments: Carrying Capacity

  • Carrying capacity is the maximum population size that a habitat can sustain over an extended period of time

  • At this point the birth and death rates are approximately equal

  • http://www.hunter-ed.com/az/course/ch9_carrying_capacity.htm

Limited environments logistic growth
Limited Environments: Logistic Growth

  • Logistic Growth is the growth pattern exhibited by a population for which growth is limited by carrying capacity, or limited availability of resources

  • Populations that achieve logistic growth are represented by a sigmoidal or s-shaped curve

  • http://gcevoices.com/ep/2012/02/10/using-logic-for-problem-solving/