Biology Revision Sheet Chapter 3 Page 62 - 80

What is Ecology?

Ecology: is the scientific study of Interactions among organisms and between organisms and their environment, or surroundings.

Biosphere: Contains the combined portions of the planet in which all of life exists, including Land, water and air or atmosphere.

Species: is a group of organisms so similar to one another that they can breed and produce fertile.

Population: are group of individuals that belong to the same species and live in the same area.

Communities: are assemblages of individuals that belong to the same area.

Ecosystem: is a group of ecosystem that has the same climate & similar dominant Communities.

 Key Point:

·         Observing is often the first step in asking ecological questions.

·         Experiments can be used to test hypothesis.

·         Modeling many ecological phenomena occurs our long periods of time or on such large spatial scales that they are difficult to study.

Chapter 3 – 2 Energy flow

Key point:

·         Sunlight is the main energy Source for life on earth.

·         Some types of organisms rely on the energy stored in inorganic chemical compounds. 

Only plants, some algae, and certain bacteria can capture energy from sunlight or chemicals and use that energy to produce food. These organisms are calledautotrophs. (Because they make their own food, autotrophs, like the help in figure 3-4 in (Page 67) are also called producers.)

During photosynthesis, these autotrophs use light energy to power chemical reactions that convert carbon dioxide and water into oxygen and energy-rich carbohydrates such as sugars and starches.

When organisms use chemical energy to produce carbohydrates, the process is called chemosynthesis.

Organisms that rely on other organisms for their energy and food supply are called heterotrophs.

Heterotrophs are also called consumers.

1.      Herbivores obtain energy by eating only plants.

2.      Carnivores, including snakes, dogs and owls, eat animals.

3.      Humans, bears, crow, and other omnivores eat both plants and animals.

4.      Detritivores such as mites, earthworms, snails, and crabs, feed on plants and animal’s remains and other dead matter, collectively called detritus.

5.      Another important group of heterotrophs, called decomposers. 

Feeding Relationship

Key Point:

ü  Energy flows through an ecosystem in one direction from the sun or inorganic compounds to autotrophs (producers) and then to various heterotrophs (consumers).

The energy stored by producers can be passed through an ecosystem along a food chain, a series of steps in which organisms transfer energy by eating and being eaten.

When the feeding relationships among the various organisms in an ecosystem form a network of complex interactions, ecologists describes these relationships as afood web.

Each step in a food chain or food web is called a trophic level.

An ecological pyramid is a diagram that shows the relative amounts of energy or matter contained within each trophic level in a food chain or food web. 

Recycling in the Biosphere

Key point:

ü  Unlike the one-way flow of energy, matter is recycled within and between ecosystems.

Elements chemical compounds and other forms of matter are passed from one organic to another and from one part of the biosphere to another throughbiogeochemical cycle.

Chapter 3—3  The Water Cycle

The process by which water changes from liquid form to an atmospheric gas is called evaporation.

Water can also enter the atmospheric by evaporating from the leaves of plants in the process of transpiration.

Nutrient Cycle

All the chemical substance that an organism needs to sustain life is its nutrients.

Key point:

Every living organism needs nutrients to build tissues and carry out essential life functions. Like water nutrients are passed between organisms and the environment through biochemical cycle.

The Nitrogen Cycle

Such bacteria, which live in the soil and on the Roots of plants called legumes, convert nitrogen gas into ammonia in a process known as nitrogen fixation.

Other soil bacteria convert nitrates into nitrogen gas in a process called denitrification.

Nutrient Limitation

Ecologists are often interested in the primary productivity of an ecosystem.

When an ecosystem is limited by a single nutrient that in scarce or cycle very slowly, this substance is called a limiting nutrient.

When an aquatic ecosystem receives a large input of a limiting nutrient- for example, runoff heavily fertilized fields – the result is often an immediate increase in the amount of algae and other producers. This Result is called an algal bloom.

To refresh your memory please go to your biology book for the figures & pictures.