Ch.24 Interactions of Life Ecology

Section 1: Living Earth A. Biosphere – the part of Earth that supports life 1. The top portion of Earth’s crust, all the waters on Earth’s surface, and the surrounding atmosphere

2. Made up of different environments that are home to different kinds of organisms For example, desert environments receive little rain Cactus plants, coyotes, and lizards are included in the life of the desert.

B. Ecosystem – all the organisms living in an area and the nonliving parts of their environment

1. Ecology is the study of interactions that occur among organisms and their environment.

2. A population is made up of all the organisms in an ecosystem that belong to the same species. 3. A community is all the populations in an ecosystem.

C. Habitat – the place in which an organism lives 1. Must provide the kinds of food, shelter, temperature, and moisture the organism needs to survive 2. Example: trees are the woodpecker’s habitat

Discussion Question What are some of the elements of your ecosystem?

What are some of the elements of your ecosystem? People Dogs Squirrels Deer Grass Trees Water Sunlight Air Soil

Section 2: Populations A. Competition – two or more organisms seek the same resource at the same time 1. Competition for food, living space, or other resources can limit the population’s size.

2. Competition is usually most intense between members of the same species.  They compete for the same food, shelter, and living space Woodpeckers must compete with each other for nesting spots.

Competition also takes place among different species. For example, after a Gila woodpecker has abandoned its nest, owls, flycatchers, snakes, and lizards might compete for the shelter of the empty hole.

B. Population size – indicates whether a population is healthy and growing 1. Population density – the size of a population

Population Size What if you wanted to compare the cricket populations in two different containers? You would calculate the number of crickets per square meter (m2) of your container. The number of individuals of one species per a specific area is called population density.

Population Size This map shows human population density.

2. Two ways to measure the size of a wildlife population…(besides counting every single organism one at a time) a. Trap-mark-release method b. Sample count method

Measuring Populations Trap-mark-release method Rabbits live underground and come out at dawn and dusk to eat. Ecologists set traps that capture rabbits without injuring them.

Measuring Populations Trap-mark-release method Each captured rabbit is marked and released. Later, another sample of rabbits is captured. By comparing the number of marked and unmarked rabbits in the second sample, ecologists can estimate the population size.

Measuring Populations Sample count method Ecologists use sample counts to estimate the sizes of large populations. To estimate the number of rabbits in an area of 100 acres, you could count the rabbits in one acre… Then multiply by 100 to estimate the population size.

3. Elements that affect population size a. Limiting factor – any living or nonliving feature that restricts the number of individuals in a population In any ecosystem the availability of food, water, living space, mates, nesting sites, and other resources is often limited.

Limiting Factors A limiting factor can affect more than one population in a community. Suppose a lack of rain limits plant growth in a meadow. Fewer plants produce fewer seeds.

Limiting Factors For seed-eating mice, this reduction in the food supply could become a limiting factor. A smaller mouse population could, in turn, become a limiting factor for the hawks and owls that feed on mice.

3. Elements that affect population size b. Carrying capacity – the largest number of individuals of one species that an ecosystem can support

If a population begins to exceed the environment’s carrying capacity, some individuals will not have enough resources. They could die or be forced to move elsewhere.

3. Elements that affect population size c. Biotic potential – the highest rate of reproduction under ideal conditions

3. Elements that affect population size d. Birth and death rates A population gets larger when… # of individuals born > # of individuals that die. A population gets smaller when… # of individuals born < # of individuals that die

e. Movement of organisms into or out of an area Most animals can move easily from place to place, and these movements can affect population size. Many bird species move from one place to another during their annual migrations.

Moving Around The seeds of dandelions, maple trees, and other plants have feathery or winglike growths that allow them to be carried by wind. Spine-covered seeds hitch rides by clinging to animal fur or people’s clothing.

C. Exponential growth – the larger a population becomes, the faster it grows  When a species moves into a new area with plenty of food, living space, and other resources, the population grows quickly Over time, the population will reach the ecosystem’s carrying capacity for that species.

Discussion Question If a population were decreasing, what kinds of questions would an ecologist ask to determine the problem?

If a population were decreasing, what kinds of questions would an ecologist ask to determine the problem? Are there any limiting factors? Is there enough food, water, living space, and mates available? Has the population reached its carrying capacity? Is something causing the death rate to increase or birth rate to decrease? Are organisms moving out of the area?

Section 3 – Interactions within Communities A. Sun – source of energy that fuels most life on Earth 1. Producers – organisms that use an outside energy source to make energy-rich molecules (their own food)

a. Most producers use the Sun and contain chlorophyll, a chemical (green pigment) required for photosynthesis

b. Some producers, found near volcanic vents on the ocean floor, use inorganic molecules as energy sources for chemosynthesis. Sulfolobes – producer bacteria

2. Consumers – organisms that cannot make their own energy-rich molecules They obtain energy by eating other organisms

a. Herbivores, such as deer and rabbits, eat plants. b. Carnivores, such as frogs, owls, and lions, eat animals.

c. Omnivores, such as pigs, bears, and humans eat both plants and animals d. Decomposers, such as earthworms, fungi, and bacteria, eat dead organisms

3. Food chain – a model that shows the feeding relationships among the organisms in an ecosystem

Food Web – all possible feeding relationships

  B. Symbiosis – any close relationship between species Mutualism – a symbiotic relationship in which both species benefit   Example: lichens Fungi  + green algae or cyanobacteria 

2. Commensalism – a symbiotic relationship in which one organism benefits and the other is not affected.  Example:  Clown fish  and sea anemone

3. Parasitism – a symbiotic relationship in which one organism benefits and the other is harmed   Exmaple  Parasitic worm  and your dog 

C. Niche – an organisms role in its environment Including: its habitat and food how it avoids danger how it finds a mate how it cares for its young

1. Predator and prey a. Predator – consumer that captures and eats other consumers b. Prey – the organism that is captured by the predator

c. Predators limit the size of prey populations, increasing the number of different species that can live in an ecosystem

2. Cooperative actions improve a species’ survival a. Example: one deer warns the others of predators in the area  stomping hoof, snorting, white tail raised while running away

2. Cooperative actions improve a species’ survival b. Example: individual ants perform different tasks required for the survival of the whole colony  worker ants, army ants, queen