Ch.50 Ecology Review Key Concepts:

1. Ch.50 Ecology ReviewKey Concepts: Dispersal and Distribution, Biotic Factors, and Abiotic Factors By Christopher Choe, Paul Bergin, Mario Gagliardo, Michael Goglia

2. Dispersal and Distribution • Dispersal is the movement of individuals away from centers of high population density, and results in broad patterns of geographic distribution. • Natural range expansions of organisms demonstrates the influence of dispersal on distribution- • Organisms move into areas where they did not previously exist. • Dispersal-a key factor in limiting distribution (depends on whether or not species transplants are successful or not)

3. Effects of DDT and other pesticides • Dispersal and distribution are greatly affected by herbicides, pesticides and other chemical products. • Dispersal and distribution normally depend upon the climate and ecosystem; the usual limiting factors are prey and predators. • Poisonous pesticides, if not immediately devastating an ecosystem, will generally pass through it by cycling. • One of their many effects include destroying food sources. This prevents the distribution of new offspring in polluted areas and causes species to move elsewhere. In addition, the areas that would ideally be used for relocation could be poisoned as well, preventing dispersal of organisms.

4. The Greenhouse Effect and Distribution of Species The greenhouse effect is the impact of heat being retained by gases in the atmosphere on the Earth’s climate. Climate change alters distribution in several ways: • Higher air temperatures increase fire risks for vegetation, and lower soil moisture. • Rising sea levels increase the amount of sea water into freshwater or wetland areas, also known as saline intrusion, which occurs mainly in estuaries. • They can also increase the frequency and size of storm surges, a type of disturbance in communities. *Only moderate disturbances can contribute positively to species. • Higher sea surface temperatures can change nutrient cycling within ecosystems.

5. Biotic Factors • Biotic factors are the living components or all the organisms that are part of an individuals environment. • Such factors may be responsible for the distribution of several species. • Species transplants, for example, can result in the species’ inability to complete a life cycle.This can be a direct result of negative interactions with other species through the form of predation, parasitism, disease, or competition, all biotic factors. • More often, predators and herbivores are the biotic factors involved in limiting distribution.

6. Effects of DDT and other Pesticides The threat that DDT poses to living organisms involves biomagnification, and it begins with microorganisms. • While microorganisms are affected by DDT, many tend to keep it inside of them rather than dying. This causes a chain reaction, as they make up the bottom of the food chain. • Likewise, many small creatures on land (ex. Earthworms) can accumulate DDT in their systems, which is harmful to predators that eat them. • In birds, DDT causes the thinning of eggshells. • Humans can also accumulate DDT in their bodies, where it is stored in fatty organs and can be extremely harmful to bodily functions • Pesticides are used to kill unwanted living things, and their effects are not limited to what they are applied. • They can affect many processes of living organisms, including growth, reproduction, neurological development, and the immune system.

7. Global Warming and Biotic Factors • Global warming is causing polar ice caps to melt, resulting in increased water levels. • Due to the lack of thermal and light energy because of the increasing depth of water in aquatic environments, marine organism populations may decrease. • Because mountain snow packs will melt earlier, probably in the spring, conditions will actually be drier when crops are most in need of the water, in midsummer. • Global warming is entailed by high ratesof climate change. Many organisms, primarily plants, won’t be able to survive the changing conditions. This is because of the rapidity of the changing climate, giving populations little time to move into areas with more suitable conditions.

8. Abiotic Factors Abiotic factors are essentially non-living components that effect the living organisms of the freshwater community. • Four abiotic factors are temperature; water, sunlight, and wind. They are the major components of climate, the prevailing weather conditions in an area. • Environmental temperature is an important factor in the distribution of organisms because of its effect on biological processes. An organismʼs internal temperature is affected by heat exchange with its environment, and most organisms cannot maintain tissue temperatures more than a few degrees above or below the ambient temperature. • The dramatic variation in water availability among habitats is another important factor in species distribution. • Sunlight provides the energy that drives nearly all ecosystems, although only plants and other photosynthetic organisms use this energy source directly. • Wind amplifies the effects of environmental temperature on organisms by increasing heat loss due to evaporation and convection. • Also, the physical structure, pH, and mineral composition of rocks and soil limit the distribution of plants.

9. Effects of DDT and other Pesticides • The effect of DDT and generally all pesticides on abiotic factors in a habitat are similar to those of acid rain. • Once DDT enters a lake, stream, or river it pollutes it, as it is a poisonous substance. Therefore, it effects water availability. • DDT is also highly persistant in soil, having the ability to last up to 15 years.

10. Acid Rain and Abiotic Factors Acid rain is precipitation containing amounts of nitric and sulfuric acid above normal levels. • Acid rain effects abiotic factors in several different ways: • Because of certain components in acid rain, toxins are mobilized, which take away several vital nutrients and minerals in soil. • The resulting decline in plants dependant on the soil will in turn affect the chain of herbivores dependant on the plants. • Acid rain can directly affect the water availability of habitats, such as lakes. • Water in lakes that becomes acidified is not available for use; it cannot support he variety of life as healthy bodies of water can.