1. Ecology 4.1 – 4.2
Eric Molina

2. Species, Communities, and Ecosystems
Species – A group of similar organisms that can
breed and produce fertile offspring
Common gene pool
Population – a group of organisms of the same
species, who live in the same area
Populations can become isolated
Isolated species might find itself evolving in a different way compared with the rest of the population

3. Autotrophs & Heterotrophs
Autotrophs – capable of making their own organic molecules as a source of food
Process involves photosynthesis
Examples of autotrophs
Cyanobacteria
Algae
Grass / Trees

4. Autotrophs
Obtain inorganic nutrients from abiotic (nonliving) environment

5. Heterotrophic Plants and Algae
Most plants and algae are autotrophs
Exceptions:
Dodder (Cuscuta europaea) feed on stems of other plants
Ghost orchid (Epipogium aphyllum) obtain carbon from fungi on the roots of living trees
Lives entirely underground till it flowers

6. Autotrophs & Heterotrophs
Heterotrophs – cannot make their own food from inorganic matter and must obtain organic molecules from other organisms
Get chemical energy from autotrophs or other heterotrophs
Examples:
Zooplankton
Fish
Sheep
Insects
Humans

7. Modes of Heterotrophic Nutrition: Consumers
Obtain chemical energy by feeding on the producers or other consumers (heterotrophs)

8. Detrivores Eat non-living organic matter (internal digestion)
Like dead leaves, feces, and dead animals (carcasses)
Earthworms, woodlice, and dung
beetle
Many bottom feeders in rivers, lakes, and oceans are detrivores

9. Saprotrophs Live on or in non living organic matter
They secrete digestive enzymes and absorb the products of digestion (external digestion)
They play an important role in the decay of dead organic materials
Fungi and bacteria

10. Communities
Is formed by populations of different species living together and interacting with each other.

11. Ecosystems Abiotic – non-living components of the environment.
Water, Air, rocks, pH, Light, relative humidity, and temperature
Biotic – Living components of the environment
A community forms an ecosystem by its interactions with the abiotic environment

12. Nutrient Cycling
There is not enough minerals to meet the needs of all the organisms in the biosphere
As a result ecosystems must recycle the carbon, nitrogen, and other elements and compounds necessary for life to exist.
Decomposers – eat waste and remains of dead
organisms
Saprotrophs and detritivores

13. Quadrat Sampling of Communities
Quadrat – a square sample area used in ecological research.
Mark out grid lines along the two edges of the area
Use a calculator of table to generate 2 random numbers and use as coordinates
Place a quadrat on the ground with its corner at these coordinates
Record the presence or absence of each species
Repeat with as many
quadrats as possible

14. Quadrat Sampling of Communities

15. Mesocosms
A small experimental area set up in an ecological research program.
Essential component
Autotrophs
Saprotrophs
Consumers & Detrivores

16. Nutrient Cycling
Decomposers recycle nutrients so that they are available to other organisms and are not locked inside the bodies or waste products of the ecosystem
Ecosystems have the potential to be sustainable over long periods of time
Have limited supplies of nutrients but they do not run out because they are able to recycle them

17. Nutrient Cycling
Nitrogen (N) is found as amino acid in all living things
Although 80 % of Earth’s atmosphere is Nitrogen gas; most organisms can only use Ammonium (NH₄⁺) and Nitric Acid (NO₃⁻)
Decomposers use digestive enzymes and convert the organic matter into a more useable form for themselves and for other organisms
Proteins from a dead organism are broken down into ammonia (NH₃) and in turn ammonia can have its nitrogen converted into useful nitrates (NO₃) by bacteria.

19. Nutrient Cycling Nitrogen Fixation
Bacteria are able to transform nitrogen into useful forms
Such as nitrates
Usable nitrates are absorbed by plants and then eaten by consumers
Nitrogen is return to the ecosystem in urea and feces

20. Energy
Plants (algae and some bacteria) that convert light energy from sunlight to the chemical energy of organic compounds. (producers)
Most ecosystems rely on a supply of energy from sunlight.

21. Energy Flow There are ecosystems that exist in total darkness.
Deep ocean water
Deep underground
Energy is converted from underwater hydro-vents

22. Photosynthesis
Photosynthetic organisms take simple organic compounds, CO₂, and convert it into energy-rich sugar, C₆H₁₂O₆.
Absorbs from the atmosphere or from water
The addition of minerals allows the producers to synthesize complex molecules such as cellulose, proteins, and lipids.
Fluxes – transfers carbon
Sinks – carbon storage in ecosystem

23. The Path of Energy and Chemicals in a Ecosystem
Every organism requires energy to carry out life’s process:
Growing
Moving
Reproducing

24. The Path of Energy
As living things use chemical energy, they release thermal energy (Heat) to the surroundings
Living (most) organisms cannot convert heat to other forms of energy

25. The Path of Energy
Energy is not recycled within an ecosystem, but flows through it and out.
Producers must continue to receive energy so they can transfer that energy; if not the ecosystem could not survive.

26. Energy Losses Food containing energy is passed along food chains.
At each successive stage less food is available and therefore less chemical energy
This is due to losses of food and energy.
Some organisms die before they are eaten
Some parts of an organism are not eaten
Some parts of an organism ingestible

27. Energy Transformations in Ecosystems
Energy Losses
Energy Transformations in Ecosystems

28. Trophic Levels Food Chains
Each species in a food chain feeds on the previous one
Producer, primary consumer, secondary consumer, and tertiary consumer (trophic levels)
Trophic level of an organism is its position in the food chain
Food chains are usually 3 to 4 trophic levels (rarely more than 5)
Only a small proportion of energy and biomass is passed to the next trophic level
Percentage is variable but unlikely to be more than 10%

29. Food Chains Trophic Level – A feeding level in an ecosystem
Food Chain – the pathway of food transfer from
one trophic level to another
Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels

30. Pyramid of Energy
A pyramids of energy is used to show how much and how fast energy flows from one trophic level to the next in a community.
The units used are energy per unit area per unit of time.
Kilojoules per square meters per year (kjm⁻²yr⁻¹)

31. Pyramid of Energy Always pyramid shaped
Each level is smaller than the one below it
This is because energy is lost at each successive trophic level
Biomass is also lost so the energy trophic level
Biomass is lost when carbon compounds are broken down by cell respiration and carbon dioxide produced is excreted
Removal of waste products of metabolism such as urea also causes loss of biomass

32. Pyramid of Energy
Pyramid of energy is a bar chart with horizontal bars arranged symmetrically.
Bars should be drawn to scale
Triangular pyramids of biomass are not appropriate.
Labels should indicate the tropic levels accurately – Start with producers, primary, secondary consumers

33. Food Webs
In an ecosystem the feeding relationship is usually more complicated than a simple food chain
Because of the variety of species; animals and
plants
Food Web – the pattern of feeding by
interconnected and branching food
chains