Population Ecology

Population Population: All the individuals of a species that live together in an area Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Three Key Features of Populations Growth Rate: Birth Rate (natality) - Death Rate (mortality) How many individuals are born vs. how many die Birth rate (b) − death rate (d) = rate of natural increase (r) Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Factors That Affect Future Population Growth Immigration + + - Population Mortality Natality - Emigration

How Do Populations Grow? Idealized models describe two kinds of population growth: Exponential Growth 2. Logistic Growth

Carrying Capacity Carrying Capacity (k): The maximum population size that can be supported by the available resources There can only be as many organisms as the environmental resources can support Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Exponential Growth Curve Figure 35.3A

Logistic Growth Curve

Factors Limiting Growth Rate Declining birth rate or increasing death rate are caused by several factors including: Limited food supply The buildup of toxic wastes Increased disease Predation

“Booms” and “Busts”

Reproductive Strategies R Strategists Short life span Small body size Reproduce quickly Have many young Little parental care Ex: cockroaches, weeds, bacteria

Reproductive Strategies K Strategists Long life span Large body size Reproduce slowly Have few young Provides parental care Ex: humans, elephants

Human Population Growth J curve growth Grows at a rate of about 80 million yearly r =1.3% Why doesn’t environmental resistance take effect? Altering their environment Technological advances The cultural revolution The agricultural revolution The industrial-medical revolution

The Human Population Doubled three times in the last three centuries About 6.1 billion and may reach 9.3 billion by the year 2050 Improved health and technology have lowered death rates

History of the Human Population