Ecology & Population Ecology Notes

Ecology

• Ecology is the study of living (biotic) and non-living (abiotic) components of the environment and their interactions.

Main Groups of Living Species:

• Producers (Autotrophs): Organisms that make their own food (self-feeders).
  • Examples: Plants, Protists, Bacteria
• Consumers (Heterotrophs): Organisms that consume other organisms (other feeders).
  • Examples: Animals, Protists, Fungi, Bacteria
• Decomposers: Break down dead plants and animals.
  • Examples: Fungi, Bacteria

Types of Producers:

• Autotrophs: Use sunlight to make food. Example: Plants (produce glucose).
• Chemotrophs: Use chemicals to make food, found in areas without sunlight.
  • Example: Certain bacteria that use hydrogen sulfide around volcanic vents.

Consumers

• Scavengers: Feed on dead organisms (detritivores).
  • Examples: Vultures, hyenas.
• Herbivores: Eat only plants.
  • Examples: Deer, rabbits, some insects.
• Carnivores: Eat only meat.
  • Examples: Lions, tigers, sharks.
• Omnivores: Eat both plants and animals.
  • Examples: Humans, bears.
• Decomposers: Absorb and break down dead material into simple nutrients.
  • Examples: Fungi, microorganisms (bacteria).

Interactions

• Community: The producers, consumers, and decomposers of an area make up a community.
  • Example: A forest community consists of trees, bacteria, fungi, foxes, rabbits, birds, etc.
• Trophic Level: Each step in the transfer of energy.

Food Chain

• A food chain illustrates what eats what and the transfer of energy from one organism to another.
• It is simple, direct, and involves only one organism at each trophic level.

Food Chain Example:

Food Web

• Food webs are interconnected food chains in a community.
• They are more complex than food chains and involve more organisms at each trophic level.
• Organisms can occupy different trophic levels in a food web based on their diet.

Food Web Structure:

• Producers: plants.
• Primary Consumers: insects, rabbits, deer.
• Secondary Consumers: birds, frog
• Tertiary Consumers/Decomposers: bob cat, fox, humans, bacteria, fungi
  *Food chains and food webs maintain balance in ecosystems.
  *Decomposers break down dead organisms for plant nutrients.

Consequences of Population Changes:

• If the rabbit population decreases, the fox population will decrease, and the plant population will increase.

Biomass

• Biomass: The total mass of organic matter at each trophic level; potential energy to be eaten and used.
• The transfer of biomass from one level to another is very inefficient; known as the 10% law.
• Only 10% of the energy from one trophic level is transferred to the next.

Ecological Pyramids

• Ecological pyramids show the trophic relationships between consumers and producers at different trophic levels.
• They indicate the amount of biomass at each level.
• Kilocalories (kcal): A unit of measurement for energy and biomass.

Example of Ecological Pyramids

• Tertiary Consumers: 1.9 kcal
• Secondary Consumers: 19 kcal
• Primary Consumers: 190 kcal
• Producers: 1,900 kcal

Biomagnification & Invasive Species

• Human activities can significantly alter ecosystems and food webs.

Invasive Species

• Invasive Species: Non-native species introduced into an ecosystem that