Populations How Populations Grow

POPULATION DYNAMICS AND CARRYING CAPACITY  Most populations live in clumps although other patterns occur based on resource distribution. Figure 8-2

Fig. 8-2a, p. 162 (a) Clumped (elephants) Clumping: -Necessary resources vary in availability from place to place -Protection from predators -Cooperation for hunting -Temporary groups for mating and caring for young

Fig. 8-2b, p. 162 (b) Uniform (creosote bush) Uniform spacing: -Better access to scarce water

Fig. 8-2c, p. 162 (c) Random (dandelions) Random: -Not common

How Populations Grow  Characteristics of Populations –Three important characteristics of a population  geographic distribution  Density  growth rate

Geographic Distribution Geographic distribution, or range, is a term that describes the area inhabited by a population.

Population Density  Population density is the number of individuals per unit area. Population density  The population of saguaro cactus in the desert plant community has a low density, whereas other plants in that community have a relatively high density.

Populations Growth  Population Growth  Three factors can affect population size: number of births the number of deaths the number of individuals that enter or leave the population. * Simply put, a population will increase or decrease in size depending on how many individuals are added to it or removed from it

Immigration & Emmigration  Immigration Immigration the movement of individuals into an area, is another factor that can cause a population to grow.  Emigration Emigration the movement of individuals out of an area, can cause a population to decrease in size.

Exponetial Growth  Exponential Growth If a population has abundant space and food, and is protected from predators and disease, then organisms in that population will multiply and the population size will increase.

Exponential Growth Exponential growthExponential growth occurs when the individuals in a population reproduce at a constant rate. Under ideal conditions with unlimited resources, a population will grow exponentially.

Logistic Growth  Logistic growth occurs when a population's growth slows or stops following a period of exponential growth. Logistic growth  As resources become less available, the growth of a population slows or stops. The general, S-shaped curve of this growth pattern, called logistic growth

Carrying Capacity  Carrying Capacity The number or the largest number of individuals that a given environment can support.

Habitat The place where an animal or plant lives and grows is called its habitat. A habitat is where and animal finds the food, water, and shelter it needs to live.

How are animal habitats destroyed? Droughts Floods Lightning and Forest Fires Land, Air, or Water Pollution Storms, Hurricanes, Tornadoes Trees are cut down to build houses, buildings, roads, furniture, and paper products. THINK: What would happen if an animal’s habitat was destroyed? Many habitats are destroyed by people or by nature.

Habitats are destroyed by... Droughts are when an area does not get rain for a long time. The ponds or streams will dry up. Most pond plants will die. Many pond animals die or move to other ponds. Some crops will not grow.

Habitats are destroyed by... Floods are when an area gets a lot of rain for a long time. Plants and animals get too much water. Many plants die. Many animals die or move to drier places.

Habitats are destroyed by... Sometimes lightening strikes a tree in a forest, causing forest fires. Plants and trees are burned and destroyed. Some animals die, others may be able to move quickly to safer places. It takes many years for a forest to grow back.

Pollution Pollution is waste that harms land, water, or air. Pollution is harmful to people, animals, the environment, and destroys many habitats. 1. Land Pollution 2. Air Pollution 3. Water Pollution

Habitats are destroyed by... Land pollution effects the land destroying life, the environment, and its habitats. Trash that people do not put in a trash can is called litter. Litter kills plants and causes animals to get sick or die. We need land to grow our food.

Habitats are destroyed by... Air pollution effects the air we breathe. Plants and animals need clean air. Factories and cars put harmful smoke and fumes in our air. Air pollution causes major damage to our health and the environment. Forests are nature’s air cleaner. We need forest to help keep the air clean.

Habitats are destroyed by... Water pollution effects the water and marine life. Water pollution destroys water habitats. Water pollution has caused animals to become endangered. All living things need clean water. Water is nature’s perfect drink! Water is a valuable resource that no one could do without.

Habitats are destroyed by... Storms Hurricanes Tornadoes

Habitats are destroyed by... Pollution Litter Construction: new houses, buildings, and roads Clearing forest to make wood and paper products. Droughts Floods Lightning and Forest Fires Storms, Hurricanes, Tornadoes PeopleNature

Think: What would happen if an animal’s habitat were destroyed?

Endangered or Extinct? The number of people in the world is growing at an alarming rate. But this is not true for all animals. In some cases, there are only a few of one type of animal left in the wild. These animals are endangered, or at risk of dying out. If they die out completely, they become extinct.

Why does this happen? There are lots of reasons why animals become endangered or extinct. The most common are: loss of habitat (forests cut down, rivers drying up). pollution poison the animals. hunting (for sport, their fur, tusks or meat).

Caring for the Environment It is in our own best interests to look after the world we live in. If a habitat is lost or damaged, it has an effect on everything. Remember - once something becomes extinct, it’s gone forever!

Think: What can you do to help the environment? Recycle means to change something so it can be used to make something new. Reuse means to use something more than once. Recycle or Reuse

Ways People Help the Environment Plant trees Recycle or reuse things Don’t litter Don’t pollute Walk or ride a bike Develop national parks Learn more about habitats Making laws to protect habitats Setting aside land for wildlife Conserve Water and other resources People can take care of their environment and keep it clean.