…Affecting Population Change

Think About This… If mice can reproduce six or more pups every six weeks, why isn’t the world covered with mice?

BIOTIC POTENTIAL  Maximum number of offspring that a species could produce if resources in an area were unlimited.  There are FOUR main factors that determine biotic potential: 1. Birth Potential 2. Capacity for survival 3. Breeding frequency 4. Length of reproductive life

1. Birth Potential Refers to the number of offspring an individual can give birth to at one time. Examples: Humans give birth to one baby at a time Whales/Elephants one baby at a time Whooping Cranes lay two eggs at a time, usually one hatches Rabbits give birth to 5-8 bunnies at once.

2. Capacity for Survival Refers to how many offspring can actually reach adulthood and reproduce. Examples: Sea turtles lay man eggs, very few offspring reach the sea and even fewer reach sexual maturity.

3. Breeding Frequency  Refers to how many times a year a species is reproducing.  Examples:  Humans can only reproduce every 9-10 months  Elk mate once a year  Rabbits mate several times a year  (Gestational period is only 30 days)  Whales 365–547 days (1-1.5 years)  Elephants 624 days ( ~2 years)  Hampster 15 days

4. Length of Reproductive Life Refers to the age that members of a species reach sexual maturity as well as the length of time they can reproduce. Examples: African Elephants become sexually mature around years of age but can successfully mate until they are 90.

Three Factors which limit populations in ecosystems 1. Limiting Factors 2. Carrying Capacity 3. Limits of Tolerance

1. Limiting Factors  Biotic Factors  Competition  Predation  Parasites  Disease  Food Availability  Abiotic Factors  Weather and climate  Habitat disruption  Light  Soil  Temperature Factors in the environment that prevent populations from attaining their biotic potential

Limiting Factor: Biotic Factor Competition Interspecific competition: Refers to competition between members of two DIFFERENT species. Example: A squirrel and a chipmunk fighting over an acorn.

Limiting Factor: Biotic Factor Competition Intraspecific Competition: between members of the SAME species. Example: Two aspen trees fighting for sunlight.

SYMBIOTIC RELATIONSHIPS Describes a relationship between two organisms in which the survival of one organism is dependent on the other. There are THREE Main Types: 1. Commensalism 2. Mutualism 3. Parasitism

1. Commensalism (+,0) One organisms benefits and the other is not significantly harmed nor helped. Example: Remora Fish attaches itself to a Shark for transportation, and eats the Shark’s “leftovers”.

2. Mutualism (+,+) Both organisms benefit Example: Pollination of Flowers Bees get food, plants are able to reproduce as bees carry pollen to another plant.

3. Parasitism One organisms benefits, the other is harmed. Example: Plasmodium parasites that cause malaria in humans. Leeches Worms – dogs & Humans (ring, tape) Parasite Types in Dogs

Biotic Factor: Predators Predator : an organism that consumes prey (organism hunted) Example: wolf hunts a deer Predator vs. Prey

2. Limits of Tolerance Law of Tolerance: States that an organism can survive within a particular range of an abiotic factor. Greater the range of tolerance the greater the organisms ability to survive.

2. Limits of Tolerance Please Draw in Notes

2. Limits of Tolerance

3. CARRYING CAPACITY Maximum number of species that can be supported by an ecosystem at a given time. Determined by the availability of resources. Insert Diagram White Board