36.5-36.6 Flashcards
What happens when the population of a species nears it carrying capacity?
Birth rate decreases; death rate increases.
What are density-dependent factors?
“a factor which causes a decline in birth rates or an increase in death rates (regulates growth) in response to an increase in population density”
What is the most common density-dependent factor?
Intraspecific competition - between those of same species.
What is an intraspecific factor?
competition between individuals of the same species for limited resources, like food supply and space for habitation. These factors affect plant growth as well.
Define physiology
study of human function
In these intraspecific factors, what is the strange development that occurs in mice when given more resources?
If a population of mices maxes out, but is given more space and resources, they will not reproduce more, as maxing out introduces a new hormone which decreases sexual maturation, etc.
What is a density-independent factor?
Factors that limit population growth, whether or not population density plays a role. Abiotic factors such as weather, fire, severe storms.
How do density-independent factors appear on graphs?
A sudden decrease in population, leveling off
List some of the factors that may reduce birth rate or increase death rate as population density increases.
Food and nutrient limitations, insufficient territories, increase in disease and predation, accumulation of toxins.
What is predation as a density-dependent factor?
as the population becomes more concentrated, predators prey on the species more.
What is a “boom” in a population?
rapid exponential growth.
What is a “bust” in a population?
When, after exponential growth, the population falls back to a minimal level.
How can the “boom and bust” cycle reflect on other populations within the ecosystem?
They can mirror each other. When hares are trapped for their pelts, and their population decreases, their main predator the lynx, also follows the boom and bust cycle.
What causes “boom and bust” cycles?
Based on an experiment with hares where extra food was provided, the most likely cause is predation, not lack of resources. Abiotic factors that influence availability of food can also do this.
In the experiment in which researchers provided hares with extra food, why was it necessary to continue the experiment for more than 20 years?
A long-term experiment was needed to detect any changes in the 10-year hare population cycle.
