1. Chapters 3-5 Biology – Miller • Levine
Ecology
Chapters 3-5
Biology – Miller • Levine

2. What is Ecology? The scientific study of:
Interactions among organisms
Interactions between organisms and their environment
Biosphere – portions of the Earth where life exists (land, water, and air)

3. Levels of Organization
Species – group of organisms that can breed and produce fertile offspring
Population – a group of individuals of the same species that live in the same area
Community – different populations that live in the same area
Ecosystem – all the organisms plus the nonliving environment
Biome – group of ecosystems with the same climate and similar communities

4. Levels of Organization

5. Energy Flow Sunlight is the main energy source for life on Earth.
Autotrophs (producers) – organisms that make their own food
Photosynthesis – use light energy to make food
Chemosynthesis – use chemical energy to make food

6. Energy Flow
Heterotrophs (consumers) – organisms that must feed on other organisms for energy
Herbivores – eat only plants
Carnivores – eat other animals
Omnivores – eat both plants and animals
Detrivores – feed on dead matter
Decomposers – break down organic matter

7. Feeding Relationships
Energy flows through an ecosystem in one direction (sun → producers → consumers)
Food chain – a series of steps in which organisms transfer energy by eating and being eaten

8. Feeding Relationships
Food web – a network of complex feeding interactions
Trophic levels – each step in a food chain or food web
1st – producers
2nd – primary consumers
3rd – secondary consumers
4th – tertiary consumers

9. Ecological Pyramids
Energy Pyramid – shows the amount of energy available at each trophic level
Only about 10% of the energy is transferred to the next level
Biomass Pyramid – shows the amount of living tissue within each trophic level
Pyramid of numbers – shows the number of organisms at each trophic level

10. Ecological Pyramids

11. Biotic and Abiotic Factors
Biotic factors – the living things that influence organisms
Abiotic factors – the nonliving things that influence organisms
Light
Soil
Wind
Water
Temperature

12. Habitat and Niche Habitat – the area where an organism lives
Niche – the role an organism plays in its habitat
No two species can share the same niche in the same habitat

13. Community Interactions
Symbiosis – any relationship in which two species live closely together
Mutualism – both species benefit (flowers & insects)
Commensalism – one species benefits while the other is neither helped nor harmed (orchids in a rainforest)
Parasitism – one organism benefits while the other is harmed (fleas on a dog)

14. Symbiosis

15. Ecological Succession
The series of changes that occurs in a community over time
Primary succession – occurs on surfaces where no soil exists (no previous life)
Pioneer species – the first species to populate the area
Lichens → mosses → grasses → shrubs → trees

16. Primary Succession

17. Ecological Succession
Secondary Succession – when a disturbance changes the existing community without removing the soil
Tornadoes, fire, clear cutting
Occurs much quicker than primary succession
Climax community – the relatively stable final community

18. Populations
Population density – the number of individuals per unit area
Population growth – increase in size of a population
Population size can be affected by:
Number of births
Number of deaths
Immigration – organisms moving into an area
Emigration – organisms moving out of an area

19. Exponential Growth
Under ideal conditions with unlimited resources, a population will grow exponentially
J-shaped curve

20. Logistic Growth
As resources become less available, the growth of a population slows or stops
S-shaped curve

21. Limiting Factors A factor that causes population growth to decrease
The population size will usually remain constant
Creates the s-shaped curve
Two kinds of limiting factors:
Density-dependent
Density-independent

22. Density-Dependent Factors
A limiting factor that depends on population size
Competition – organisms compete for resources
Between members of the same species
Between members of different species
Parasitism and disease

23. Density-Dependent Factors
Predation – when one species feeds on another
Predator – the organism that feeds on the prey
Prey – the organism being eaten

24. Density-Independent Factors
Affects all populations, regardless of the population size
Unusual weather – heavy storms
Natural disasters – tornado, volcanic eruption
Seasonal cycles – insects die during winter
Human activities – clear-cutting forests

25. Human Population Growth
At first the human population grew slowly
About 500 years ago it started increasing rapidly
Resembles the J-shaped curve
US & World
Populations