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Ecology 2483 > Lecture 9 > Flashcards

Lecture 9 Flashcards

1
Q

Human Pipulation Growth

A
  • Humans have a large impact on the global environment
  • Our population has grown explosively
  • Along with our use of energy and resources
  • For thousands of years, our population grew relatively slowly
  • reaching 1 billion for the first time in 1825
  • Now we are adding 1 billion people every 13 years
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2
Q

Ecological Fooptprint

A
  • Total area of productive ecosystems required to support a population
  • Data used on agricultural productivity, production goods, resource use, population size, and pollution
  • Area required to support these activities is then estimated
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3
Q

Introduction

A
  • “no population can increase in size forever”
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4
Q

A Growth Capacity for Rapid Population Growth

A
  • The limits imposed by a finite planet restrict a feature of all species
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5
Q

What do Ecologists try to Understand

A
  • try to understand the factors that limit or promote population growth
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6
Q

Population Dynamics

A
  • The ways in which populations change in abundance over time
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7
Q

Population Size Changes as a Result of

A
  1. Birth
  2. Death
  3. Immigration
  4. Emigration
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8
Q

Equations:

A
  • see notes
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9
Q

Geometric Growth

A
  • If a population reproduces in synchrony at discrete time periods and growth rate doesn’t change
  • Geometric and exponential growth can lead to rapid increases in population size
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10
Q

Population Increase by Constant Proportion

A
  • The number of individuals added is larger with each time period
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11
Q

Growth Rate (λ)

A
  • ratio of population size in year t+1 (Nt+1) to population size in year t (Nt )
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12
Q

Lamda (λ)

A
  • geometric growth rate or per capita finite rate of increase
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13
Q

Exponential Growth

A
  • When individuals reproduce continuously, generations can overlap.
  • If a population is growing geometrically or exponentially
    - a plot of the natural logarithm of population size versus time will result in a straight line
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14
Q

dN/ dt

A
  • rate of change in population size at each instant in time
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15
Q

R

A
  • exponential population growth rate or per capita intrinsic rate of increase
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16
Q

In Natural Populations

A
  • favourable conditions result in exponential growth, but it CAN NOT continue indefinitely
  • There are limits to population growth
17
Q

Effects of Density

A
  • Population size can be determined by density-dependent and density-independent factors
18
Q

Effects of Density Under Ideal Conditions

A
  • λ > 1 for all populations
  • But conditions rarely remain ideal
  • λ fluctuates over time
19
Q

Density-Dependent Factors

A
  • Decrease population size at higher population
    1. Birth
    1. Death
    1. dispersal rates change as the density of the population changes
20
Q

As density increases

A
  • birth rates often decrease
  • death rates increase
  • dispersal (emigration) increases
  • all of which tend to decrease population size
21
Q

Population Regulation

A
  • Density-dependent factors cause population to increase when density is low and decrease when density is high
  • Food, space, or other resources are in short supply and population size decreases
  • Density-independent factors can have larger effects on population size
    - Do not regulate population size
22
Q

Density- Independent Factors

A
  • Effects on birth and death rates are independent of the number of individuals in the population:
    • Temperature and precipitation, catastrophes such as floords or hurricans
      - Warming drys up soil and extends growing seasons and leads to less snowfall
  • Illegal poaching the primary cause of a decline in elephant population growth rate in Africa
23
Q

Logistic Growth

A
  • Population increases rapidly, then stabilizes the carrying capacity
  • Growth rate decreases as population nears carrying capacity ( since resources begin to run short)
24
Q

At Carrying Capacity

A
  • the growth rate is 0
  • the population does not change
25
Q

The Logistic Equation

A
  • Assumes that r declines as N increases
  • When densities are low, logistic growth is similar to exponential growth
  • As density increases, growth rate approaches 0 as population nears K
26
Q

Age Structure

A
  • characterizes a population
  • the proportion of the population in each age class
27
Q

Age Structure Influences How Fast a Population Will Grow

A
  • If there are many people of reproductive age (15 to 30), it will grow rapidly
  • A population with many people older than 55 will grow more slowly
    • Rapid Growth: Nigeria
    • Negative Growth: Japan
28
Q

Survivorship Curve

A
  • Plot of the number of individuals from a hypothetical cohort that will survive to reach different ages
29
Q

Survivorship Curve can be Classified into 3 General Types

A
  1. Type I
  2. Type II
  3. Type III
    - Birth and death rates can vary greatly between individuals of different populations of the same species
30
Q

Type I

A
  • most individuals survive to old age - Ex. Dall sheep, humans
31
Q

Type II

A
  • the chance of surviving remains constant throughout the lifetime
    Ex. some birds
32
Q

Type III

A
  • High death rates for young, those that reach adulthood survive well (species that produce a lot of offspring)
    Ex. most organisms
33
Q

Life Tables

A
  • Can be used to predict age structure and population size
  • can also be based on size or life cycle stage
34
Q

Ix (survivorship)

A
  • number of survivors divided by the original number of individuals
35
Q

Fx (fecundity)

A
  • average number of offspring a female will have at age x
36
Q

If Survival or fecundity Rates Change

A
  • the population growth rate, and age distribution will change
37
Q

In some Species, Age is not Important

A
  • reproduction is more dependent on size (related to growth conditions) than age
    Ex. many plants

Ecology 2483 (21 decks)

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