1. Ecology
PART I

2. Lesson Objectives
Describe ecological levels of organization in the biosphere.
Distinguish between abiotic and biotic factors.
Define organism, population, community, ecosystem, biome, and biosphere as the terms are used in ecology and other ecological concepts.
Define limiting factors and their effect on population dynamics.
Compare and contrast niches and habitats.

3. Introduction
Ecology is the study of interactions of living things with each other and their environments.

4. Levels of Organization
Ecologists study organisms and their environments at different levels of organization:
Biosphere: consists of all organisms on Earth

5. Biome: group of ecosystems that have the same climate and dominant communities.
Ecosystem: consists of living things and their environment.

6. Community: consists of populations of different species that live in the same area and interact together.
Population: organisms of the same species that live in the same area, interact with one another, and produce fertile offspring.

7. Organisms: are individual living things.
This is the lowest level of organization that ecologists study. Biologists study organisms, organ systems, organs, tissues, cells, organelles, and molecules. Chemists study atoms and subatomic particles.

8. Organisms and the Environment
Organisms: life form consisting of one or more cells; has characteristics of life.
Environment includes both living (biotic) and nonliving things (abiotic).

9. Biotic and Abiotic Factors
Biotic living organisms
Abiotic nonliving or physical factors
Together determine productivity of the ecosystem in which organisms’ live

10. What Is a Population?
In biology, a population is a group of organisms of the same species that live in the same area. How large a population is and how fast it is growing are often used as measures of its health.

11. Limits to Population Growth
limiting factor is a property of a population’s environment – living or nonliving – which controls the process of population growth. Biologists have identified two major types of limiting factors:
Density-dependent factors
Density-independent factors.
Density-dependent limiting factors depend on population size and include competition, predation, parasitism, and disease. Density-independent limiting factors affect all populations regardless of population size and include unusual weather, natural disasters, seasonal cycles, and certain human activities, such as, damming rivers, and clear-cutting forests.

12. What Is a Community?
Communities are made up of populations of different species. A community is the biotic part of an ecosystem. It consists of all the populations of all the species in the same area. It also includes their interactions.

13. What Is an Ecosystem?
An ecosystem is a unit of nature and the focus of study in ecology. It consists of all the biotic and abiotic factors in an area and their interactions. Ecosystems can vary in size. A lake could be considered an ecosystem. So could a dead log on a forest floor. Both the lake and log contain a variety of species that interact with each other and with abiotic factors.

14. Ecosystem Components
Niches
Habitats
Competitive Exclusion Principle

15. The Niche
Niche organism’s occupation (role), where it lives, and way in which organism’s use conditions they exist in
Food it eats
Place in food web
How it gets food
Range of temperatures
needed for survival
When and how it
reproduces
No 2 species share the same niche or habitat, can occupy niches that are similar
Habitat where an organism lives

16. The Habitat
Physical environment to which an organism has become adapted and survives in.

17. Competitive Exclusion Principle
Two different species
cannot occupy the
same niche in the
same geographic area.
If they do they will compete
with one another for the
same food and other resources.
Eventually, one species will
out compete the other.

18. Biomes and Climate
Climate is the average weather in an area over a long period of time. Weather refers to the conditions of the atmosphere from day to day.
In terms of moisture, climates can be classified as arid (dry), semi-arid, humid (wet), or semi-humid. The amount of moisture depends on both precipitation and evaporation.
Biomes are categorized based upon their climate types.

19. Climate and Biodiversity
Climate determines plant growth, it also influences the number and variety of other organisms in a terrestrial biome. Biodiversity generally increases from the poles to the equator. It is also usually greater in more humid climates.

20. Climate and Adaptations
Organisms evolve adaptations that help them survive in the climate of the biome where they live. For example, in biomes with arid climates, plants may have special tissues for storing water. The desert animals also have adaptations for a dry climate. In biomes with cold climates, plants may adapt by becoming dormant during the coldest part of the year. Dormancy is a state in which a plant slows down cellular activities and may shed its leaves. Animals also adapt to cold temperatures. One way is with insulation in the form of fur and fat.

21. Survey of Terrestrial Biomes
Terrestrial biomes are classified by climatic factors and types of primary producers.

22. Aquatic Biomes
Terrestrial organisms are generally limited by temperature and moisture. Therefore, terrestrial biomes are defined in terms of these abiotic factors. Most aquatic organisms do not have to deal with extremes of temperature or moisture. Instead, their main limiting factors are the availability of sunlight and the concentration of dissolved oxygen and nutrients in the water.

23. Aquatic Biomes and Sunlight
In large bodies of standing water, including the ocean and lakes, the water can be divided into zones based on the amount of sunlight it receives:
1. The photic zone extends to a maximum depth of 200 meters; enough sunlight penetrates for algae and other photosynthetic organisms to photosynthesize.
2. The aphotic zone is water deeper than 200 meters; too little sunlight penetrates for photosynthesis to occur. As a result, food must be made by chemosynthesis or else drift down from the water above.

24. Aquatic Organisms
Aquatic organisms generally fall into three broad groups: plankton, nekton, and benthos. They vary in how they move and where they live.
1. Plankton are tiny aquatic organisms that cannot move on their own. They live in the photic zone. They include phytoplankton and zooplankton. Phytoplankton are bacteria and algae that use sunlight to make food. Zooplankton are tiny animals that feed on phytoplankton.
2. Nekton are aquatic animals that can move on their own by ‘‘swimming” through the water. They may live in the photic or aphotic zone. They feed on plankton or other nekton. Examples of nekton include fish and shrimp.
3. Benthos are aquatic organisms that crawl in sediments at the bottom of a body of water. Many are decomposers. Benthos include sponges, clams, and anglerfish which are adapted to a life in the dark.