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Transcript
Population Principles
Chapter 3
1
•
Population Characteristics
Population - Group of individuals of the
same species inhabiting the same area
simultaneously. (6.4 Billion – 2004)
– Natality and Mortality
 Natality ________________________________
________________________________
 Birth Rate (Humans Born / 1,000)
– Mortality __________________________________
 Death Rate (Humans Died / 1,000)
2
Figure 7.1
3
Population Characteristics
•
Population Growth Rate ___________________________________.
Often expressed as a percentage of the total
population. (Geometrically – Population)(Arithmetically
– Food Supply)
•
Survivorship Curve - Shows proportion of
individuals likely to survive to each age.
– High mortality in young.
– Mortality equitable among age classes.
– Mortality high only in old age.
4
Survivorship Curve
(Fig.7.2)
5
•
Sex Ratio and Age Distribution
Sex Ratio - Age Distribution
– Sex Ratio __________________________________
_________________________________.
 Females determine the number of
offspring produced in sexually
reproducing populations.
– Age Distribution __________________________________
_________________________________.
 Greatly influences population growth
rate.
6
Age Distribution in Human Populations
(Fig.7.3)
7
Population Density and Spatial Distribution
•
Population Density ___________________________________
___________________________________.
– High population may lead to increased
competition for resources.
 Dispersal - Movement of individuals
from densely populated locations to new
areas.
 Emigration - Movement from an area.
 Immigration - Movement into an area.
8
Population Growth Curve
•
Biotic Potential ___________________________________
___________________________________
___________________________________
– Generally, biotic potential is much above
replacement level.
 Natural tendency for increase.
 All living populations follow an
exponential growth curve.
9
Exponential Growth Curve
•
•
•
Lag Phase ___________________________________.
Exponential Growth Phase (Log Phase)___________________________________
___________________________________
________________________. *Currently*
Stable Equilibrium Phase ___________________________________
___________________________________
___________________________________
10
Biotic Potential (Fig.7.4)
11
Typical Population Growth Curve (Fig.7.5)
12
Carrying Capacity
•
Carrying Capacity ___________________________________
___________________________________
___________________________________.
13
Environmental Resistance
•
Environmental Resistance ___________________________________
___________________________________
___________________________________.
– Four main factors:
 Raw Material Availability
 Energy Availability
 Waste Accumulation and Disposal
 Organism Interactions
 Disease, Predation, and Space
14
Carrying Capacity (Fig.7.6)
15
Bacterial Growth Curve (Fig.7.7)
16
Fig. p.138
17
Reproductive Strategies
and Population Fluctuations
•
Not all species reach a stable carrying
capacity.
– Species can be broadly lumped into two
categories:
 K-strategists
 r-strategists
18
K - Strategists
•
•
•
•
•
•
•
Large organisms
Long-lived
Produce few offspring
Provide substantial parental care
Populations typically stabilize at a carrying
capacity.
Usually occupy relatively stable
environments.
Reproductive strategy is to invest in a few,
quality offspring.
19
K - Strategists
•
•
Controlled by density-dependent limiting
factors.
– Factors that become more severe as the
size of the population increases.
 Diseases
Deer - Lions - Swans
20
r - Strategists
•
•
•
•
•
•
•
Small organisms
Short-lived
Produce many offspring
Little if any parental care
Usually do not reach carrying capacity
(boom-bust cycles).
Exploit unstable environments.
Reproductive strategy is to produce large
numbers of offspring to overcome high
mortality.
21
r - Strategists
•
•
Controlled by density-independent limiting
factors.
– Population size is irrelevant to the limiting
factor.
 Weather Conditions
Grasshoppers - Gypsy Moths - Mice
22
Population Cycles (Fig.7.8)
23
Human Population Growth
•
Major reason for increasing human
population growth rate
is__________________________________
___________________________________
___________________________________
_
24
Historical Human Population Growth
(Fig.7.9)
25
Doubling Time
•
Doubling Time of a Population (years) :
•
70 / Population Growth Rate (%)
( 70 / 2.0% = 35 years )
26
Doubling Time for the Human Population
(Fig.7.10)
27
Human Population Growth
•
Interactions Affecting Carrying Capacity
– Available Raw Materials
– Available Energy
– Waste Disposal
– Interaction With Other Organisms
28
Social Factors Influence Human Population
•
Humans are social animals who have
freedom of choice.
– People make decisions based on history,
social situations, ethical and religious
beliefs, and personal desires.
 Biggest obstacles to controlling human
population are not biological, but are the
province of philosophers, theologians,
politicians, and sociologists.
29
Ultimate Size Limitation
•
•
If the world continues to grow at current rate,
population __________________________.
Human population subject to same biological
constraints as other species.
– Human population will ultimately reach a
carrying capacity and stabilize.
 Disagreement about exact size and
primary limiting factors.
30
Elephant Trade
31
Snow Goose
(Pg.145)
32