Ecology 5.docx

Definitions **Need to Know all definitions** Ecology is the study of the interrelationship of plants and animals with each other and with their environment. An ecosystem refers to organisms and their interactions with their environment. Biosphere is all the parts of the earth where life exists. Habi...

Definitions **Need to Know all definitions** Ecology is the study of the interrelationship of plants and animals with each other and with their environment. An ecosystem refers to organisms and their interactions with their environment. Biosphere is all the parts of the earth where life exists. Habitat is the place where a species lives. Abiotic Factors are non-living features of the environment. Edaphic Factors are abiotic factors relating to soil. Biotic Factors are influences of living organisms on each other. Every species has its own set of conditions that it requires. These are called environmental factors. They include abiotic and biotic factors and vary greatly depending on whether the environment is terrestrial (land) or aquatic (water). Each species has adaptations to its environment, Adaptations are the features of an organism that allow it to have a better chance of survival in its habitat. Environmental factors affecting living organisms Biotic Factors - Feeding: If a species is used as food by another species, then its population will be reduced. If a species that is used as food is plentiful, then the consumer will become more numerous as it will be able to produce and feed more young. - Disease: Disease is generally caused by other living things. Disease usually reduces populations, sometimes very significantly. - Pollination: The transfer of pollen from an anther to a stigma. Carried out by insects such as bees. If bees are scarce, then pollination is not as successful and the number of seeds produced will dop, which will affect the plant population. - Nitrogen-fixing bacteria: Important in maintaining soil fertility. Found in the root nodules of leguminous plants and free-living soil. Replace nitrates used by the plants. - Decomposers: Break down the remains of dead plants and animals to the soil to be reused. Abiotic Factors - Climatic Factors: a. Light intensity has a major influence on the distribution of plants and some animals. Daisy’s only grow in areas where there is strong light exposure. Bluebells can photosynthesise in very little light and will grow only in areas with a lot of shade. b. Temperature is important in controlling the rate of chemical reactions. Temperatures vary very little in large bodies of water. Organisms living in water tend to be far less tolerant to heat changes. A 5oC change in temperature can kill a fish as it has no mechanisms to adapt to these changes. c. Exposure to the elements is another factor in coastal systems. Plants that live in the intertidal zone are exposed to large changes in their environment up to four times a day. They have many adaptations to survive the changes in its environment. - Edaphic Factors: a. pH is the measure of acidity or alkalinity of the soil. pH affects the availability of nutrients to the plants. Most plants like neutral to slightly alkaline soils. b. Mineral Content is determined by the underlying bedrock. Minerals are vital for plant growth. c. Water content is important because the minerals are obtained from the soil while they are in solution, if there is insufficient water, the soluble minerals will not be available. The plants will wilt, and photosynthesis will be reduced. Too much water can deprive the roots of oxygen and reduce growth. d. Humus is a dark organic substance made from decaying plant and animal material. It provides a good source of nutrients for plants and increases the ability of the soil to retain moisture. Abiotic Factors **Need to know examples from terrestrial and aquatic habitat of each factor** Factor Effect Example Altitude Higher altitudes are cooler, wetter, windier than lower altitudes Trees cannot live at very high altitudes. Aspect (i.e., direction a surface faces) North-facing slopes are cooler and darker than south-facing slopes. More plants grow on south-facing slopes. Steepness Steep slopes lose water quickly and soils are washed away. Conifers can grow on steep slopes (because their leaves lose very little water). Climatic Factors Factor Effect Example Temperature Affects the rate of reactions in living things. Higher temperatures cause rapid plant growth in summer. Lower temperatures cause hibernation in hedgehogs and frogs in winter. Humidity (amount of water vapour in the air) High humidity reduces evaporation. Woodlice are restricted to the humid conditions within decaying leaves. Day length Affects plant flowering and germination along with migration, hibernation, and reproduction in animals. Many plants produce flowers due to the longer days in spring. Swallows migrate due to shorter autumn days. Light intensity Affects the rate of photosynthesis. Trees grow tall to get more light. Wind Causes physical damage. Increases evaporation. Trees exposed to wind grow better on the sheltered side and appear to lean away from the wind. Helps spread spores and some pollen and seeds. Edaphic Factors Factor Effect Example Soil pH Plants and animals are adapted to specific pH values. Acid soil (e.g., Bogs) have a pH less than 7, and support bog moss and heather. Neutral soils have pH values close to 7 and are preferred by most plants. Alkaline soils have pH values greater than 7, and are preferred by lime-loving plants e.g., birdsfoot trefoil and bee orchid. Soil type (determined by particle size) (a) sand (large particles) Good drainage and air content. Low mineral and water content. Few earthworms in sand (no humus to eat). (b) clay (small particles) Impermeable to water and air. Easily waterlogged. Plants do not grow well, as the soil is too wet and difficult for roots to penetrate. Organic matter (humus) Decaying organic matter (humus) provides food, helps bind soil particles, retains water and minerals Vital to plant life. Provides food for organisms such as earthworms. Water content Absorbed by roots. Plants need to absorb water for transpiration, photosynthesis, and general metabolism. Minerals dissolve in water and are absorbed by roots. Air content Provides oxygen for roots, microorganisms, and animals. Lack of oxygen in soil prevents plant and animal growth. Mineral content Needed by plants. A lack of mineral causes stunted growth and yellowing of leaves – chlorosis. Aquatic habitats have special problems compared to terrestrial habitat. These problems include: - Light penetration: Plankton grow best in the upper layers of water due to higher light intensity. - Currents: move organisms, Plants & animals are washed away. Need for attachment (e.g., limpets and many seaweeds). - Wave action: moves and damages organisms - Salinity: Salt content means organisms adapt to freshwater or saltwater. Causes problems with water moving in or out of organisms and their cells. Limpets live in seawater, not freshwater. Organisms in seashore ponds must be able to withstand changes in salinity (due to rainfall and evaporation). - Oxygen: in lower concentration. - Tides: length of time organisms are exposed or submerged. Shore plants lose water when tide is out. Organisms on shores have shells or mucilage to retain water.