Download 5 Populations and Limits on Populations

Previous Questions
p27 #1-4
p29#1-4
p35 #1-6, 9-15
Check understanding
ALL ABOUT POPULATIONS
Learning Goals

By the end of this lesson I should be able to…
 describe
the factors that affect the population size of a
species.
 Explain the difference between open and closed
ecosystems.
 Describe three types of interactions in a biotic
community
Factors that Affect Population Size

Natality or Births per year

Mortality or Deaths per year

Immigration: Number of individuals moving into a population.

Emigration: Number of individuals moving out of a population.
Open vs. Closed Populations


Open Populations: Affected by all 4 factors.
Closed Populations: Only affected by Births and
Deaths.
Limits on Populations
Factors that contribute to limiting the size of a
population.
Biotic Potential

Maximum number of offspring that a species could
produce if there were NO limiting factors.
4 Limiting Factors that affect
Biotic Potential




Birth Potential: Maximum number of offspring per birth.
Capacity for Survival: Number of offspring that reach reproductive
age.
Procreation: Number of times a species reproduces each year.
Length of Reproductive Cycle: Age of sexual maturity and the
number of years an individual can reproduce.
Remember gestation periods
http://www.mnn.com/earth-matters/animals/photos/12-animals-with-the-longest-gestation-period/elephants
Limiting Factors - Prethinking
Biotic potential is often never reached because not all
conditions are ideal. Some factors that would limit
biotic potential include:





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Environmental Limiting Factors


Biotic: Food availability, number of predators,
diseases and competition for resources.
Abiotic: Sunlight, Temperature, Precipitation.
Carrying Capacity

The MAXIMUM number of individuals of a species that
can be supported by an ecosystem (determined by
availability of resources)
CAUSES of Changes in Population Size

Density-dependent factors: Affect a population
BECAUSE of size.


Eg. Food, competition for mates, water, resources, disease
and predation
Density-independent factors: Affect a popualtion
REGARDLESS of size.

Eg. Flood, fire, drought, destruction of habitat
Community (Biotic) Interactions
Interactions among organisms that help to shape
the ecosystem in which they live.
THREE MAIN TYPES OF INTERACTIONS
Competition, Predation, and Symbiosis
http://www.youtube.com/watch?v=CsfJL-IIVz4
1. Competition

More than one organism tries to use a resource at the
same time, in the same place.
Can between same species or different species.
 Species often adapt to have different niches.
 Increases as population size increases.

2. Predation

http://www.youtube.com/watch?v=CsfJL-IIVz4
When one organism eats another organism to
obtain food.
 Prey
have developed ways to avoid being eaten
(physical, camouflage, tasting repulsive, mimicry)
 Predators have developed ways to catch prey quicker
(speed, eyesight, claws)
2. Predation Continued…

Can affect a population by:
 Bottom-up:
Starts at the bottom. (Primary consumer eats
too many plants…)
 Top-down: Starts at the top. (Top carnivore eats too
many rabbits)
3. Symbiosis

Symbiosis- A surprising tale of species cooperation
Relationship in which two species live closely
together. Three main categories:
 Parasitism:
One species benefits at the expense of the
other species.
Parasitism
Introduced parasite fungus
https://www.youtube.com/watch?v=_lWQLd5U0g8
Note that humans have moved and introduced all kinds of parasites
to new locations and often when introduced for the first time the
organisms have no defense!
3. Symbiosis

Commensalism: One species benefits while the
other is neither helped nor harmed.
3. Symbiosis

Mutualism: Both species benefit.
 Eg.
Leaf-cutter ants and fungus….
Practice
p42 #1-3 and
p46 #3,4,6
to check understanding