Organisms in Their Environment
Understanding ecosystems, populations, and environmental factors
Living Together
How organisms interact with their environment
Habitat
The place where an organism lives, with specific environmental conditions (temperature, moisture, light, etc.)
Example: A woodlouse lives in a habitat under rotting logs - dark, damp, cool
Ecosystem
A community of living organisms (biotic) interacting with their non-living (abiotic) environment
Example: A pond ecosystem includes fish, plants, bacteria (biotic) plus water, rocks, sunlight (abiotic)
Population
All the individuals of one species living in a particular area at a particular time
Characteristics: Population size, density, distribution pattern
Community
All the different populations (different species) living together in an ecosystem
Example: Oak trees, squirrels, birds, insects, fungi living together in a forest
Niche
The role and position of an organism in its ecosystem: where it lives, what it eats, how it reproduces, its relationships
Example: A bee's niche includes pollinating flowers, collecting nectar, living in hives
Biotic Factors (Living)
Food availability
Prey, plants, nutrients for growth
Predators
Animals that hunt and eat other organisms
Competition
Other organisms competing for same resources (food, space, mates)
Disease & Pathogens
Bacteria, viruses, fungi causing illness
Symbiotic relationships
Mutualism, parasitism, commensalism
Abiotic Factors (Non-living)
Temperature
Affects metabolic rate, enzyme activity
Light intensity
Essential for photosynthesis in plants
Water availability
Needed for all life processes
pH level
Acidity/alkalinity of soil or water
Oxygen concentration
For respiration in animals and plants
Soil type & minerals
Nutrients for plant growth
Abiotic Factors (Non-living)
Biotic Factors (Living)
Resulting Populations
65
Plants
24
Herbivores
7
Predators
Observations
- More light and water → More plants
- More plants → More herbivores can survive
- More herbivores → More predators can survive
- More predators → Fewer herbivores survive
Quadrat Sampling
Using a square frame (quadrat) to count organisms in a defined area
- Place quadrat randomly in study area
- Count number of organisms inside
- Repeat multiple times for reliability
- Calculate mean and estimate total population
Transect Walk
Systematic sampling along a line to see how species change across an area
- Stretch a tape measure across study area
- Place quadrats at regular intervals along line
- Record species at each point
- Shows distribution patterns (e.g., from pond edge to center)
Question: Describe the ecosystem and niche of an oak tree in a forest
Ecosystem Description:
The oak tree is part of a woodland ecosystem. The community includes other trees (beech, birch), shrubs, grasses, insects, birds, squirrels, fungi, and decomposers. Abiotic factors include soil type (rich in minerals), rainfall (moderate), temperature (temperate climate), and sunlight (filtered through canopy).
Niche of Oak Tree:
- Position: Dominant canopy tree, tall with spreading branches
- Nutrition: Autotroph - makes food by photosynthesis using sunlight, water, CO₂
- Reproduction: Produces acorns (wind-pollinated flowers), dispersed by animals
- Relationships: Provides habitat for birds, insects, squirrels; food source (acorns, leaves); shelter from predators
- Resource use: Deep roots access water; large leaves capture sunlight; shades ground below
Key Concept: The oak tree's niche describes its complete role in the ecosystem - not just where it lives, but how it survives, reproduces, and interacts with other organisms.
Term
Habitat
Which of these is an abiotic factor?