Download Factors Affecting Population Change

yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

Source–sink dynamics wikipedia, lookup

Storage effect wikipedia, lookup

Human overpopulation wikipedia, lookup

The Population Bomb wikipedia, lookup

World population wikipedia, lookup

Maximum sustainable yield wikipedia, lookup

Molecular ecology wikipedia, lookup

Theoretical ecology wikipedia, lookup

Factors Affecting
Population Change
Exponential Vs. Logistic Growth
Two Strategies for Growth
1. “r-strategists”: Spawners!
Characterized by exponential growth, which results
in temporarily large populations, followed by
sudden crashes in population size.
Ex. Insects, bacteria, some plants
live in unpredictable and rapidly changing environments
 Reproduce quickly when conditions are favorable
 External Fertilization
 Many offspring: small, mature rapidly, no parental care
Two Strategies for Growth
2. “K-strategists”: Brooders!
Characterized by a high degree of specialization.
Ex. Trees, whales, tigers, etc.
Live in stable and predictable environments
 Can compete effectively
 Reproduce late in life
 Internal Fertilization
 Few offspring: large, mature slowly, often much parental
Density Dependent Factors
 Factors that influence population regulation,
having greater impact as population density
increases or decreases
Struggle for survival includes factors like competition,
predation, disease, and other biological effects
Density Dependent Factors
 Intraspecific
Competition –
Ecological interaction
where individuals of the
same species/population
compete for resources in
their habitat.
Density Dependent Factors
 Predation -
Consumption of prey
by carnivores
-Regulation can occur due to
preferred species of prey
Density Dependent Factors
 Disease –
Pathogens able to pass
from host to host in
overcrowded populations
with greater ease
Density Dependent Factors
 Allee effect –
Occurs when population
cannot survive or fails to
reproduce enough to
offset mortality once the
population density is too
low; such populations
usually do not survive.
Eg. The extinct
passenger pigeon.
Density Dependent Factors
 Minimum viable
population size –
Smallest number of
individual needed for
a population to
continue for a given
period of time
Small population size
can result in inbreeding
and loss of genetic
Density Independent Factors
 Factors influencing population regulation
regardless of population density
Human intervention – Pesticides…Climate change
 Environment - reproductive success based on
temperatures, natural disasters etc
Limiting Factors
 Any essential resource
that is in short supply
or unavailable. These
factors determine how
much the individual or
population can
Eg. light, space, water,
 Classify each of these as either
density-dependent or densityindependent. Share with a
classmate – do you agree or
diagree? Why? [I][C]
A drought decreases the water level
of a lake, thus decreasing its
carrying capacity.
Lynx prey on snowshoe hares. An
increase in the snowshoe hare
population caused an increase in the
lynx population.
Due to the introduction of a new
species of fish, a lake becomes
crowded and some species do not
Increased water temperature causes
many aquatic organisms to die.
 Why might the birth and death
rates of a white-tailed deer
population in the Carolinian
forest of southern Ontario be a
density-dependent factor?