p27 #1-4p29#1-4

p35 #1-6, 9-15Check understanding

Previous Questions

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.

Factors that contribute to limiting the size of a population.

Limits on Populations

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 - PrethinkingBiotic potential is often never reached because not all conditions are ideal. Some factors that would limit biotic potential include:  

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

Interactions among organisms that help to shape the ecosystem in which

they live.THREE MAIN TYPES OF INTERACTIONS

Community (Biotic) 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

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)

http://www.youtube.com/watch?v=CsfJL-IIVz4

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

Relationship in which two species live closely together. Three main categories: Parasitism: One species benefits at the

expense of the other species.

Symbiosis- A surprising tale of species cooperation

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….

p42 #1-3 and p46 #3,4,6

to check understanding

Practice