Title: BIOL 4120: Principles of Ecology Lecture 9: Properties of Population
1BIOL 4120 Principles of Ecology Lecture 9
Properties of Population
- Dafeng Hui
- Room Harned Hall 320
- Phone 963-5777
- Email dhui_at_tnstate.edu
2Population Ecology
- What is a Population?
- What constitutes an individual?
- Easy for most large sexually reproducing animals
(humans, dogs, cats etc) - Not so easy for colonies of animals and many
plants - Trees (Ramets)
- Coral
- Unitary or modular
Aspen seagrass
3- Properties of Population
- Most important property is abundance of
population which is determined by its
distribution and density. - Populations have
- Distribution
- Density
- How to determine population density?
- Age structures
- Different sex ratios along time
- Changes in distribution and density due to
dispersal, emigration, immigration and migration. - Distribution and density change in both space and
time
49.1 Distribution of a population
- Distribution
- Spatial location, Area over which a species
occupies - Geographic range
- Area that encompasses the entire population of a
species - Limited by climate
- Direct temperature, precipitation
- Indirect
- Food production
- Water supply
- Habitat
- Incidence of parasites, pathogens and competitors
- Geographic barriers
5- Influenced by available habitat
- Temperature
- Red Maple
- -40oC
- Carolina wren
- Northwards -7oC
- Westwardgt52mm
- When all environmental factors within its range
of tolerance, the organism can live in its
habitat - Horned lark
- Avoids forests
- Available territory
6Tiger Beetle of Cold Climates
79.2 Distribution of a species varies at different
spatial scales
Continental scale climate suitability Particular
area microclimate and stream banks (coniferous
trees and abundance) Within a particular
locality occupy stumps of conifer trees (pH is
acidic) Local subpopulations
Distribution of moss Tetraphis
89.3 Abundance reflects both population
distribution and density
- Abundance (number of individuals in a population)
- distribution area population Density
- Density can be a key factor
- Number of individuals per unit space
- Distribution patterns
- 1. Random Equal chance of being anywhere.
- 2. Uniform distribution of resources.
- Regular Uniformly spaced.
- Exclusive use of areas.
- Individuals avoid one another.
- 3. Clumped Unequal chance of being anywhere.
- Mutual attraction between individuals.
- Patchy resource distribution.
9Distribution of Individuals on Small Scales
10(No Transcript)
119.4 How to measure density?
- Direct Counts
- Time consuming
- Needs to be sure you can see all individuals in
the area - 1. Quadrates
- Organisms must be static
- Needs laying of quadrates to be random
- Statistical analysis essential
- 2. Mark and recapture
- Estimate
- Assumes equal chance of capture for all
- No deaths or births
- Marked animals random among unmarked
- No loss of marks
- No emigration or immigration
- Other factors include time of capture, stress of
capture, sex, age, etc. - Additional sampling methods
- The presence of an individual can be determined
by tracks, bird song, etc - Get a relative measure
Sampling
12Capture-recapture or mark-recapture methods
- Lab
- Suppose there is a population with size (N),
trap, mark and release a known number of marked
animals (M) - After a period of time (well mixed with other
animals) - A sample of population with sample size (n) is
re-captured. Among these, (R) animals are marked. - Assumption M/NR/n
- NnM/R
- Example M39 rabbits, n151934, R15
- N3439/1588
139.5 Populations have age structures
Age structure the number or proportion of
individuals in different age groups
Age pyramids for three human populations in 1989.
14- Techniques used for aging animal populations
- Mark young individuals and follow their survival
- Study a representative sample
- Tooth wear
- Plumage changes
- Growth rings in teeth, horns, ear bones, and so
forth
15Some plant ages can be determined too
Mark, DBH, ring
Tree rings show annual growth (American beech,
Fagus grandifolia)
16- In plant populations, the distribution of age
classes is often skewed because dominant
overstory trees may inhibit the establishment of
seedlings or the growth and survival of juvenile
trees
17An oak forest in England
189.6 Sex ratios in populations shift with age
- In theory, populations of sexually reproducing
organisms tend toward a 11 sex ratio (males to
females) - In mammalian pop.,
- at birth 1.05
- lt15 1.04
- 15-65 1.02
- gt65 0.81
- CIA 2006 data. (See slide showed before)
19Sex ratio changes with age groups age pyramid
20- Sex ratios in populations shifts with age
- Humans
- More males at birth
- Males have shorter life span
- War
- High risk activities
- Females need to survive giving birth to children
219.7 Individuals move within and among populations
- Movement of individual will influence the
sub-population density - Dispersal
- Emigration
- Immigration
22- Dispersal movement of individuals in space.
- Method of dispersal
-
- Passive dispersal (gravity, wind, water, animal)
seeds of plants, small animals, fish, shrimp.
fruits and seeds ate and carried by animals (long
distances) -
- Active dispersal animal movement,
- Emigration an individual moves out of a
subpopulation - Immigration an individual moves from another
location into a subpopulation
23Migration a round trip
- Migration A round trip, perhaps involving
mating - Red-necked ducks
- Breeding in the north east
- Winter in South Carolina and Florida
- Gray whale
- Winter in California,
- Summer in Arctic
Migratory pathways of Ring-necked ducks and gray
whale.
249.8 Distribution and density change in both space
and time
- Distribution and density of population change
with space and time - Primary factors driving the dynamics of
population abundance are the demographic
processes of birth and death. - Many causes such as dispersal, immigration,
emigration, and temporal changes in environmental
conditions.
25Invasive species
Gypsy moth caterpillars
Defoliated oak forest
764 M loss in 1981
26Invasive species
Kudzu, an invasive species
Native to Asia, introduced to US as an ornamental
vine in 1876 Used to control soil erosion in
1930s and 1940s 1950s, recognized as pest Cover
southeastern US, 2 million to 7 million acres
27The END