lu4 population growth and life table (final) Flashcards
Population definition
a group of…
a group of individuals of the same species in
each area (habitat).
Ecology definition
organisms
the study of how organisms interact with each
other and their environment.
Population ecology definition
s&d o p
the branch of ecology that studies the structure & dynamics of populations.
The term “population” is interpreted differently in various sciences: (3)
pop eco, human demo, genetics
- In population ecology - a group of individuals of the same species inhabiting the same area.
- In human demography - a set of humans in a given area.
- In genetics - a group of interbreeding individuals of the same species, which is isolated from other groups
8 characteristics of a population
AS, 3D, GF/R, M, N, S
- Size: no. of individuals in the population
- Density: number of individuals in each area
- Distribution: the spread of individuals in each area
-
Dispersion: how it spreads to other locations (clump,,
uniform, or random) - Age structure: pre-reproductive, reproductive, postreproductive
- Natality: birth rate
- Mortality: death rate
- Growth forms/ growth rate: r-selected or K-selected
2 factors affecting natality & mortality:
ACoP, En
1) Age composition of population
2) Environment
* Not all members of the population are equal in their ability to survive
& reproduce.
Density-dependent factor
__ impact as pop ___/___ increase
- Population growth rates are regulated/influenced
- limited by the density of a population.
- Is any factor influencing or limiting population growth
- Greater impact as population size/density increases.
5 examples of density-dependent factor
- Competition for space which restrict population growth.
- Limited food supply which restricts reproduction.
- Predators concentrate in area where there is a lot of prey.
-
High densities may cause stress, hormone changes & immune
protection level. - Diseases
what is density-independent factor
- Any factor influencing population regulation that acts to reduce population by the same percentage, regardless of size.
- By chance
3 examples of density-independent factor
- Weather
- Climate
- Natural disasters
what is biotic Potential (or Growth Rate), r
max rate, pop could……inc, ideal conditions
The biotic potential is the maximum rate at which a population could increase under
ideal conditions.
Biotic Potential; 4 rsns WHY each species will have a different biotic potential?
V/FoR/LS/SR
DUE TO:
* variations in the species’ reproductive span (how long an individual is capable of reproducing)
* the frequency of reproduction (how often an individual can reproduce)
-> Semelparous: one reproductive event per lifetime
-> Iteroparous: multiple events per lifetime
* “litter size” (how many offspring are born each time)
* survival rate (how many offspring survive to reproductive age)
Exponential Growth
(Continuous population
growth in an unlimited
environment) can be
modeled as exponential
population growth.
Density-dependent Growth vs. Exponential Growth
- Populations will not increase forever. Ignoring all interactions with other species (competition, predation, parasites, herbivory), resources will still limit growth - food resources & space resources.
- If exponential growth continued, we would be swimming in several meters of houseflies in just 10 years
4 limits to Population Growth
BP, LR,Cp(K), LG(curve)
- Few populations can live up to their biotic potential; = where conditions are ideal, every member has food, shelter, no predators or pathogens in the environment, maximum reproduction
- Over time, the limiting resources of an environment will limit the population growth
- Population size will reach the carrying capacity (K)
- Resulting in Logistic growth (S-curve)
(Characteristics of Density-dependent Growth) Carrying capacity =
and what can limit them (2)
the maximum number of
individuals of a species
that can be sustained by an
environment without
decreasing the capacity of
the environment to sustain
that same amount in the
future
Resources will limit growth
- Food and/or Space
Population Strategies
r-Strategy Compared to K-Strategy
- r-strategy: high intrinsic growth rates - focuses on reproduction, not on competition with other individuals in the population.
- K-strategy: focuses on population at or near carrying capacity - must be able to compete with other individuals in the population.
6 characteristics (each) of contrasting reproductive strategies
- Extrinsically Controlled Growth
-> r-strategy
1. Short life
2. Rapid growth
3. Early maturity
4. Many small offspring
5. Little parental care or protection
6. Little investment in individual
offspring - Intrinsically Controlled Growth
-> K-strategy
1. Long life
2. Slower growth
3. Late maturity
4. Fewer large offspring
5. High parental care and protection
6. High investment in individual
offspring
r-K scale of reproductive strategy: balancing egg output vs parental care
- oysters = r-strategy
– produce 500 mil fertilized eggs per year
– provide no parental care - great apes = K-strategy
– produce 1 infant per 5 or 6 years
– provide extensive parental care
life tables
- Show how survival & reproductive rates vary with age,
population size or life cycle (developmental) stage - Information about births & deaths is essential to predict
trends or future population size - Also provide data for Mortality & Survivorship Curves
survivorship curve
- A survivorship curve is a plot of the no. of individuals from a
hypothetical cohort that will survive to reach different ages
(data obtained from life table). - Survivorship curves can vary:
– among populations of a species
– between males & females
– among cohorts that experience different environmental
conditions - Survivorship curves – 3 general types
3 types of survivorship curves graphs
- type I: high death rate in post-reproductive years (keatas kanan)
- type II: constant mortality rate throughout life span (gradient)
- type III: very high early mortality but the few survivors then live long (stay reproductive) (kebawah kiri)
Life Expectancies/ Survivorship Change With Age (I,II,III types)
example
s, mortality rate
-
Type I:
̶ humans & other large mammals, giant tortoise
̶ high mortality when reach old age
̶ K-strategy -
Type II:
̶ birds (seagull, songbird), small mammals, reptiles
̶ probability of death is unrelated to age -
Type III:
̶ aquatic organisms that release fertilised eggs,
invertebrates, plants (annual & perennial)
̶ high mortality of very young individuals
̶ r-strategy
Summary: Population Growth
- It is also important to consider human growth patterns when
studying the population growth & decline of other species because:
1. Humans out compete most species for many resource- food, water, land, etc. Thus their carrying capacity is dramatically affected
2. Increase in human populations cause the amount of toxic to build up (pesticide run off, cargo ship oil spills, acid rain)
3. Some species get benefits from the growth of human population. eg: - house sparrows & cockroaches use human shelters for homes
- bacteria & amoebae’s can use humans as an intermediate host intheir life cycle
- lice, thrive in humans
- Thus no matter what the species, humans have an impact of their ability to
survive and reproduce.
