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In this section

• 1. Organic Matter
• 2. Diversity
• 3. Photosynthesis
• 4. Interdependence
• 5. Development
• 6. Biomes

Summary

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Contents

Organic matter

1. Aims
2. The biosphere consists of all the plants and animals which are present on Earth
3. The biosphere is part of the wider ecosphere
4. Organic matter includes and depends on a range of chemical elements
5. Macronutrients and micronutrients are essential for plant growth
6. Standing crop, productivity and biomass each have distinct meanings
7. Primary productivity is the conversion of solar energy into organic matter by photosynthesis
8. Carbon gets into the biosphere by assimilation (as carbon dioxide) by green plants in photosynthesis
9. There is considerable global variability in biomass and net primary productivity
10. Human activity has substantially reduced global primary productivity
11. Nutrient cycles are movements of individual chemical constituents
12. An abundant supply of nitrogen in a form that plants can take up is of vital importance
13. Uptake of nutrient elements occur either through roots or through cell walls
14. Nutrient uptake in plants occurs by two mechanisms, passive or active
15. The products of assimilation are either ingested by animals or are broken down by micro-organisms

Diversity

1. Aims
2. Biologists use the term biodiversity quite generally to encompass the overall variety of life
3. There are increasing concerns about the loss of biodiversity in ecological systems
4. Taxonomy and systematics are the disciplines devoted to naming and classifying living things
5. There are currently five recognised kingdoms
6. Viruses have no separate kingdom
7. Living things are highly organised; there is a series of levels
8. Organisms do not occur in isolation
9. Biologists categorise themselves according to the level of organisation they study
10. Reproduction is vital for species survival
11. The simplest form of reproduction is asexual
12. Sexual reproduction occurs via the fusion of male and female organs
13. Sexual reproduction may facilitate more rapid evolution than asexual reproduction
14. A life cycle is the sequence of changes that occurs in the life of an organism

Photosynthesis

1. Aims
2. Organisms modify the environment by photosynthesis and respiration
3. In photosynthesis a plant will capture light with chlorophyll
4. Land plants interact with their immediate environment via their roots, and the stomata in their leaves
5. Plants need sunlight to photosynthesise
6. Light and water are both critical to the process of photosynthesis
7. Aquatic plants will grow wherever there are sufficient nutrients and light for them to prosper
8. Availability of nutrients controls plant growth
9. The organic matter of plants and animals is broken down in the air by respiration
10. The most important single source of organic matter for decomposition on land is leaf litter
11. During the decomposition of organic matter by bacteria, simple organic acids are produced
12. There are corresponding decomposition processes for aquatic ecosystems
    

Interdependence

1. Aims
2. Organisms live together in ecological communities and interact with each other
3. Some species interactions are beneficial; others are neutral; others are harmful
4. Mutual dependence between species takes many forms
5. Different species often share the same resource base
6. Food webs and food chains represent trophic (feeding) relationships
7. Elton's pyramid of numbers describes the abundance of primary producers and consumers
8. The inter-relationships within a food web can be summarised via trophic levels
9. A feature of all food webs is the relatively few trophic levels that are present
10. Energy transfer between trophic levels in the sea (as on land) is very inefficient
11. A predator is any species which uses another species, the prey, as a source of food
12. No species is preyed upon too heavily
13. Predators and their prey exert restrictions on each others' distribution
14. The snowshoe hare and the lynx can exist in dynamic equilibrium
15. The kaibab deer have been observed to diminish in the absence of natural predators
16. There is positive feedback between the kaibab deer and their food sources
    

Development

1. Aims
2. Each species has a distinct optimum point on each factor gradient
3. Stress affects the physiological well being of plants
4. Specialisation is the evolutionary adoption of special characteristics
5. Single plants cope with stress quite differently from communities of plants
6. An ecosystem is a collection of species, interacting with the abiotic environment
7. Stable ecosystems can last for a long time
8. Microclimate greatly influences very localised ecosystem conditions
9. Microhabitat is the immediate subsurface environment of an ecosystem
10. Succession is the sequential development of changes within a plant community
11. There are three major theories of succession
12. A sere is the sequential development of one or more plant communities
13. When a sere reaches the end of its succession it is said to have reached a climax state
14. A plagioclimax occurs as a result of human interference
15. The succession of development by subseres is known as the secondary succession
16. The concepts of succession, seres and climax are of immediate practical importance

Biomes

1. Aims
2. Biomes is an imprecise term
3. The opinions of ecologists differ as to the exact definition of biome
4. Ecologists have devised a list of biomes
5. Biomes may also be defined by altitude
6. The tropical rain forest biome can be found in an area known as the wet tropics
7. Tropical grasslands or savanna areas experience great variability in precipitation and temperature
8. Deserts are characterised by extreme water shortage and a wide range of temperature
9. Chaparral forms in mild temperate regions which have a Mediterranean type climate
10. Temperate grasslands occur in areas with dry summers and low winter temperatures
11. Temperate forests are characterised by deciduous trees and abundant secondary flora
12. Taiga is the coniferous forest which lies north of the temperate forest zone
13. Tundra regions are characterised by low temperatures, dark winters and strong winds