Population Ecology Chapter 9 G T Miller Jr. Shohail Motahir Choudhury

Sea Otters: Back from Extinction

Population Dynamics What are the major characteristics of a population? Population dynamics is the study of how populations change. Populations change in size, density, and age distribution.

What are the major characteristics of a population?

Population dynamics is the study of how populations change.

Populations change in size, density, and age distribution.

Three general patterns: clumping, uniform distribution, and random dispersion. Most species live in clumps or groups. Population Distribution

Why Clumping? Availability of resources varies from place to place. Living in groups offers better protection from predators. Some predator species live in packs to better have a chance to get a meal . Temporary groups may form for mating and caring for young. Uniform pattern distribution may occur where a resource, such as water, is scarce.

Availability of resources varies from place to place.

Living in groups offers better protection from predators.

Some predator species live in packs to better have a chance to get a meal .

Temporary groups may form for mating and caring for young.

Factors Governing Population Size Births and Immigration Deaths and Emigration Population Change = (Births+Immigration)- (Deaths+Emigration)

Factors limiting population growth No Population can grow indefinitely because resources Light Water Nutrients Biotic Potential. Housefly: 5.6 trillion within 13 months. Within few years can cover the earth’s entire surface. (Intrinsic rate of increase (r). Nature limits population growth. Environmental resistance . Together biotic potential and environmental resistance determine the carrying capacity (K).

Population Size Growth and Decrease Factors Growth factors (biotic potential) Favorable light Favorable temperature Favorable chemical environment (optimal level of critical nutrients) Abiotic High reproductive rate Generalized niche Adequate food supply Suitable habitat Ability to compete for resources Ability to hide from or defend against predators Ability to resist diseases and parasites Ability to migrate and live in other habitats Ability to adapt to environmental change Too much or too little light Temperature too high or too low Unfavorable chemical environment (too much or too little of critical nutrients) Abiotic Low reproductive rate Specialized niche Inadequate food supply Unsuitable or destroyed habitat Too many competitors Insufficient ability to hide from or defend against predators Inability to resist diseases and parasites Inability to migrate and live in other habitats Inability to adapt to environmental change Decrease factors (environmental resistance) Biotic Biotic

Exponential vs logistic growth

Reindeer introduction in south coast of Alaska. 26 8 Sheep introduction in Tasmania.

Types of population fluctuations

Predation in Controlling Population Size Top-down Bottom –up Interaction between predation and food supplies.

Human Impacts on Ecosystems Habitat degradation and fragmentation Ecosystem simplification Genetic resistance Predator elimination Introduction of non-native species Overharvesting renewable resources Interference with ecological systems

Learning from Nature Principles of sustainability Solar Energy Nutrient Recycling Population Control Biodiversity

Next Class Energy Efficiency and Renewable Energy Chapter 18 G T Miller Jr. Shohail Motahir Choudhury Poster Presentation: February 21