LECTURE #2 How Ecosystems work Unit 8: Ecology

The ultimate source of energy on earth is the sun The ultimate source of energy on earth is the sun. We cannot use the sun’s radiant energy directly to power our cells however.

The sun’s energy must be transformed by producers (photosynthesis) into a usable form. Review from last semester: What is the name of the ‘food’ that they make??

This usable form (glucose) is then passed up through whatever feeding relationships exist in the ecosystem.

Nature has 3 basic ‘job descriptions’ Job #1 Producer- organisms that first capture energy Examples: Plants, some kinds of bacteria, blue-green algae What do producers make? Answer: Energy storing molecules How do they trap the sun’s energy? Through what process? What is that process similar to in animal cells?

Producers are also known as autotrophs; organisms who make their own food.

Primary productivity the rate at which organic material is produced by photosynthetic organisms in an ecosystem. What factors affect primary productivity?

Factors that affect the rate of photosynthesis Amount of sunlight Amount of Carbon Dioxide Amount of Water Temperature

Ecological Importance - Producers make up the base of all feeding relationships on earth! The producers support all other organisms on earth by providing them directly or indirectly with the energy they need to run their cells. Without producers, life wouldn’t be possible on earth.

Job Description #2 Consumer Consumers – organisms that consume plants or other consumers to obtain the energy necessary to build their molecules.

Consumers are also known as heterotrophs; organisms that get their energy by consuming other organisms.

Are these guys autotrophs or heterotrophs?

Trophic Pyramid- A graphic organizer that shows the feeding relationship of groups of organisms, and the distribution of biomass or energy among different trophic levels in a given ecosystem.

Trophic Level – a group of organisms that have the same source of energy. This is represented by a step in a food chain. Food Chain - the path of energy through the trophic levels of an ecosystem.

Marine Food Chain Arrows point in the direction that the energy is moving. Note to student: Food chains are oversimplified. In most ecosystems, organisms often occupy more than one trophic level.

Food web - a network of interconnected food chains in an ecosystem.   Food webs are a much better representation of feeding relationships in ecosystems because they show that organisms may feed at multiple trophic levels.

Marine Food Web

A Food Web Describes the Way Energy is Transferred Within an Ecosystem Ecology 9/18/2018 A Food Web Describes the Way Energy is Transferred Within an Ecosystem G. Podgorski, Biol. 1010

How trophic levels are organized The 1st Tropic Level is made up of Producers This is the base of the pyramid. There is more available energy at this level than any other.

Tropic Level 2 is made up of Primary Consumers; organisms that feed exclusively from The 1st tropic level. Herbivores – Animals that eat plants or other Primary producers. Examples - elk, deer, rabbit

Tropic Level 3 is made up of organisms known as Secondary consumers Tropic Level 3 is made up of organisms known as Secondary consumers. Carnivores - Animals that eat other animals. Examples – tigers, wolves, snakes

What do you call an organism that eats plants and animals? Omnivore – Organism that eats plants and other animals. Examples – humans, bears (except polar bears), pigs

4th trophic level - composed of carnivores that consume other carnivores. These organisms are known as tertiary (3rd order) consumers.

How many Trophic Levels does an Ecosystem Typically Have? It is very rare for an ecosystem to have more than four trophic levels. Why do you think that is?

Answer: There is hardly any energy left once it passes up through the 4th trophic level. The amount of available energy limits the number of trophic levels in an ecosystem.

Job #3 Recycling Crew Decomposers – organisms that cause decay. Ecological Importance- Decomposition releases nutrients back into the environment to be recycled by other organisms.   Examples: Bacteria and Fungi

Decomposers get energy from all trophic levels. Everything dies eventually, right?

These guys also help recycle waste Detritivores- Organisms that feed on detritus, or organic waste . Examples- worms, millipedes, vultures

Celebrating Rot and Decay - Detritivores Ecology 9/18/2018 Celebrating Rot and Decay - Detritivores Energy isn’t transferred only upwards between trophic levels. Detritovores use the energy available in dead organisms and allow recycling of essential nutrients in ecosystems. G. Podgorski, Biol. 1010

Take 2 minutes to summarize what you have learned about the three ‘Job Descriptions’ on earth and how they are interdependent on one another.