Science 1206

Unit 01 Section 02 – Lesson 01Ecology

In this lesson you will:

• define ecology and ecosystem

• distinguish between biotic factors and abiotic factors and describe examples to illustrate each

• explain how abiotic factors affect the sustainability of the ecosystem

• describe examples to illustrate biotic interactions

• describe ways that organisms respond to changes in environmental conditions

• describe symbiotic relationships including: mutualism, commensalism, parasitism, and predation

• describe trophic structure in terms of food chains and food webs

• explain how biotic and abiotic factors affect ecological interactions and the distribution of organisms

• Ecology – is the scientific study of the interactions of organisms and

their environment. – Interactions of organisms and their environment refers to the

way the organism affects the environment as well as how the environment affects the organism

• Ecosystem – is a community of organisms and the physical environment in

which it lives.– When an ecologist studies the organisms living in a forest and

includes a study of the physical factors that affect the organisms in the forest, then the ecologist is studying an ecosystem.

– Example

• Abiotic factors are the nonliving factors which affect life in any ecosystem.

– Space • All organisms require enough space or territory to insure

adequate resources to food, water, shelter, and mates.

– Temperature• Environmental temperature affects biological processes and

the ability of most organisms to regulate their temperature.

– Oxygen • Most living organisms require oxygen for cellular respiration,

which is a process that releases energy from food.

– Sunlight • Sunlight is the ultimate source of energy for all photosynthetic

organisms which in turn provide the resources for other living things (in most ecosystems).

Examples:

– Water • Water (humidity) is necessary for all life. The ability to find water,

to maintain water balance, and to conserve water help determine the habitat range for each species.

– Inorganic and Organic Soil Nutrients –• Inorganic soil nutrients

– include minerals such as phosphates, nitrates, potassium, magnesium and

– a host of other minerals derived from rocks. • Organic nutrients

– include organic compounds in humus which promote the growth of bacteria, fungi, and a host of other organisms beneficial to the soil.

• The physical structure, water holding potential, pH, and nutrient level of soil limit the distribution of plants and in turn the animals that inhabit a terrestrial region.

• The composition of the substrate in a stream affects the chemistry of the water above and in turn affects plant and animal life living there. the type of substrate also influences what animals can attach to or burrow in (especially in the intertidal zone).

Biotic factors

• refer to the living environment and include all other organisms that interact with the individual both of the same species and all other species.

• Biotic factors also includes – decomposing animals and

plants (detritus)– Disease– predator/prey interactions– Competition– symbiotic relationships

(symbiosis).

• Detritus – refers to decomposing plant and animal materials including

their dead bodies as well as their wastes. – Bacteria and fungi living in the ecosystem help to break down

the materials within the detritus and recycle these materials back to the plants.

• Disease – is the result if infection by fungi, bacteria, virus, and other

pathogens. – Disease is an important biotic factor because disease tends to

reduce the number of organisms within the community.

• Predator/prey interaction – is another important biotic factor which helps to limit the size

of populations within an ecosystem.– There is a balance between the number of predator and prey

in any ecosystem.

• Competition – is a struggle for survival that occurs between two organisms

either of the same or different species.– Competition tends to limit the size of the population keeping it

in balance with the available resources.

Symbiotic relationships:• Symbiotic relationships are biotic relationships in which two different

organisms live in close association with each other to the benefit of at least one.

• There are five types of symbiotic relationships including:

1. Mutualism2. Commensalism3. Parasitism4. Parisitoidism5. predation.

1. Mutualism – mutual benefit to both of the organisms

in the relationship. • Ex: hummingbird and flower

2. Commensalism– one organism benefits from the

relationship but the other organism seems to neither be harmed nor benefited. • example to illustrate commensalism

is the beaver and the fish. • Finding Nemo!

– Clownfish live within the waving mass of tentacles of sea anemones; Because most fishes avoid the poisonous tentacles, the clownfish are protected from predators.

3. Parasitismone organism benefits and the other is

harmed. • The organism that benefits is called

the parasite, the organism that is harmed is called the host.

• Some parasites only cause slight damage to their host, while others kill them. • Ex: tapeworms

4. Parisitoidism– is similar to parasitism. One

organism benefits but the other is eventually killed - a sort of slow death. • An example of parisitoidism is when

a female wasp stings a spider causing paralysis but not death. The wasp then lays a single egg on the spider. When the egg hatches into a larva, it slowly eats the body of the spider eventually killing it - but slowly.

5. Predation • is where the interaction is

beneficial to one species and detrimental to the other.

• This is not always considered a symbiotic relationship, although it is quite similar to parasitism, except for the degree of harm to the host or prey. With predation, the prey is killed. • An example of predation is

when a lion kills a zebra and eats it as its source of food.

Trophic Structure:

• Trophic structure– refers to the feeding relationships within the ecosystem.

– five trophic levels 1. primary producers2. primary consumers3. secondary consumers4. tertiary consumers,5. decomposers (also known as detritivores).

– The various organisms that comprise each of the trophic levels determines the flow of energy and the cycling of materials within the ecosystem.

– Feeding relationships are generally viewed as a food web consisting of all the possible food chains that exist within the ecosystem.

– Since the primary producers are the only photosynthetic organisms, they determine the amount of energy (trapped from the sun) that can be passed up through the food web.

– The detritivores enable the recycling of materials and are therefore the organisms that are the foundation for biogeochemical cycling.

1. Producers or Autotrophs

– green plants, that produce their own food.

– They make organic compounds (food such as sugar) from inorganic compounds (carbon dioxide and water) by photosynthesis.

– The ultimate source of energy for life on Earth is the sun.

• Solar energy is trapped during the process of photosynthesis and converted into a chemical form that we normally call food.

• The materials within the food are recycled. They pass from the producers to the consumers and finally are recycled back to the producers by the action of the decomposers.

• Energy, unlike the materials, is not recycled.

• As the food is passed through the food web, most of the energy is lost.

– Pyramid of energy - about 10% of the energy stored in one trophic level (such as producers) is actually transferred to the next trophic level (for example the herbivores).

– Which means that 90% of the energy is lost.

– Eventually there is so little energy remaining in the top trophic level that no higher trophic level can be supported.

– This should explain why there are fewer fourth order consumers in an ecosystem as compared to the primary consumers.

HOW?

2. Consumers or Heterotrophs

– Organisms that obtain nutrients from other organisms.

– They cannot make their own food so they must obtain it ready made.

– Two types of carnivores.

1. Predators - hunt and kill other animals for food.

2. Scavengers - are animals that feed on the dead bodies of other organisms.

3. Decomposers – are organisms of decay.

– These are also called saprobes.

– They are generally fungi or bacteria that break down the complex compounds in the remains of dead animals and plants, producing simple substances that can be used again by the producers.

– Decomposers are therefore very important because they recycle materials within the ecosystem.

– The decomposers are the final consumers in any ecosystem

• Herbivores – are animals that feed only on plants.– Rabbits, cattle, horses, sheep

• Carnivores – are animals that feed on other animals. – Some carnivores may be predators (such as lions, hawks, and

wolves who attack and kill their prey and feed on their bodies) and some may be scavengers (they feed on dead animals that they find).

• Omnivores – These are animals that feed on both

plants and animals. – Examples of omnivores are humans

and bears.

• Saprobes – Organisms that get nutrients by

breaking down the remains of dead plants and animals, or their wastes.

– Examples of saprobes are bacteria and fungi.

– Saprobes are also known as decomposers are an essential component of any ecosystem. Their main role is to recycle nutrients in dead organisms and their wastes.

– Without the decomposers to recycle nutrients, there could be no life since plants would run out of nutrients.

Review• Read 1.12 "Roles in Ecosystems" on pages 40-44. • Answer questions 1-4 from "Understanding Concepts" and

"Exploring" on page 44.