An introduction to ecology and the biosphere
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An Introduction to Ecology and the Biosphere. Chapter 50. Ecology and Evolutionary Biology.

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Ecology and Evolutionary Biology

  • Darwin’s extensive observations of the distribution of organisms and their adaptation to specific environments led him to propose that environmental factors interacting with variation within populations could cause evolutionary change.

  • Events that occur in the framework of ecological time (minutes, months, and years) translate into effects over the longer scale of evolutionary time (decades, centuries, millennia, and so on).- Example: Hawks feed on field mice have an immediate impact on the prey population by killing individuals, and reducing population size. (Ecological effect) This also alters the gene pool. (Evolutionary effect)


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Organisms and the Environment

  • The environment of any organism includes:Abiotic- Nonliving components; chemical and physical factors such as temperature, light water and nutrients.Biotic- Living components; all the organisms (biota) that are part of the environment. - Other organisms may compete for resources, prey upon others, parasitize others, provide food, or change the physical and chemical environment.

  • Example: Studies suggest that an abiotic factor, the amount and variability of precipitation, influences the distribution of red kangaroos in Australia. - Are the controls on red kangaroo distribution only abiotic? Multiple factors could affect patterns of distribution and abundance; for example climate could be indirectly affecting red kangaroo distribution through biotic factors such as pathogens.


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Subfields of Ecology

  • Organismal ecology - concerns how an organism’s structure, physiology, and behavior meet the challenges posed by the environment.- May be subdivided into the disciplines of physiological, evolutionary, and behavioral ecology.

  • Population ecology -concentrates mainly on factors that affect how many individuals of a particular species live in an area.

  • Community ecology - (an assemblage of populations of many different species) deals with the whole array of interacting species in a community. -Focuses on how interactions such as predation, competition, and disease, as well as abiotic factors such as disturbance, affect a community structure and organization.

  • Ecosystem ecology - (consists of all abiotic factors in addition to the entire community of species that exist in a certain area) the emphasis is on energy flow and chemical cycling among the various biotic and abiotic components.

  • Landscape ecology - deals with arrays of ecosystems and how they are arranged in a geographic region.- Consists of a mosaic of different types of “patches”, referred to as patchiness.- Focuses on the factors controlling exchanges of energy, materials, and organisms among the ecosystem patches making up landscape or seascape.

  • Biosphere – the sum of all the planet’s ecosystems (the global ecosystem).- This broadest area of ecology includes the entire portion of Earth inhabited by life.


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Ecology and Environmental Issues

  • To address environmental problems, we need to understand often complicated and delicate relationships between organisms and the environment. The science of ecology provides that understanding.

  • Most of societies awareness of environmental issues began in1962 with Rachel Caron’s Silent Spring. (Spread awareness of the harms of DDT)

  • Many influential ecologists recognize a responsibility to educate legislators and the general public about decisions that affect the environment.

  • Although our ecological information is always incomplete, we must make decisions about environmental issues. Given what we do know about the interconnectedness of the biosphere, it is wise to follow:The precautionary principle- “An ounce of prevention is worth a pound of cure”.


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---->Briefing on DDT<----

  • DDT is an extremely strong and lethal pesticide. In the past it was used greatly during WW2 to stop mosquitoes from spreading malaria. It was a cheap pesticide that was believed to have a low toxicity to mammals. Then problems /of DDT began to appear. DDT entered the food chain and got stored in the fatty tissues of the animals. In 1972 many people acknowledged and realized the long-lasting effects of DDy and it was banned.


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Section 50.2 - Interactions between organisms and the environment limit the distribution of species.

The study of the distribution of organisms past and present is called biogeography. There are several factors that influence (limit) an organism’s distribution.

1) dispersal: the movement of individuals away from high population or area of origin. Dispersal can be seen when organisms move to areas where they didn’t exist previously. This is called natural range expansion. Another way in which dispersal can be seen is through species transplants. Species that are moved to a new area must not only survive but reproduce.

2) behavior: One such behavior that can limit distribution is habitat selection. Animals and plants both have habitat selection behavior. An example is female insects that only deposit eggs in response to certain stimuli.

3) biotic factors: Do other species limit distribution? Other species can limit the distribution of a certain species through predation, parasitism, disease, or competition, or a species can be limited if another species which they depend on is missing from the new habitat.

4) abiotic factors: temperature, water, sunlight, wind, and rocks and soil. Temperature affects biological processes and internal temperatures. Water affects distribution in that organisms depend on either salt or freshwater. Sunlight drives nearly all ecosystems because of the energy it provides. It is also very important in aquatic ecosystems and to organisms that are sensitive to photoperiod (daytime and nighttime). Wind effects temperature (increase heat loss) and water loss (increase rate of evaporative cooling). Rocks and soil can affect water chemistry.

5) climate: Climate affects the distribution of species in that it varies in particular areas. For example, a species that needs to live in waters of a fairly warm temperature can’t be swimming in the arctic where the waters are very cold. Furthermore, seasonality affects distribution. For instance, birds fly south or north depending on the season.


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How DDT Affects the Distribution of Organisms environment limit the distribution of species

  • DDT is a pesticide that can be lethal in certain quantities. It could affect organisms by limiting and perhaps even allowing distribution. The simplest way DDT can limit the distribution of organisms is by killing a large portion of a species at its original habitat. Obviously, if the animal is dead from DDT, it cannot move and disperse itself. In addition, if a species was relocating to a new habitat that had been infected with DDT, it would be killed at the new habitat, perhaps before it had any chance of reproducing.

  • It was mentioned that biotic factors such as other species limit distribution. If at a new habitat DDT had killed a certain predator, then a new species that would have been prey at the new habitat can move to this new location. Instead of being killed by the predator and being removed from the new habitat, the species can prosper there. Also, if a species’ habitat was sprayed with DDT, and the species was able to detect that their habitat had been infected, the species could move to a new habitat to avoid death.


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Distribution is effected by population increase. environment limit the distribution of species

  • Distribution is effected by population increase because as population increases, animals of the same species will begin to cause too much competition for resources in an area. This causes some animals to explore new regions in search of a suitable place to live and reproduce that is not as overpopulated.

  • Population increase can also aid small populations in becoming more established. This causes the species to become more distributed among a certain area. This can also create more prey or predation (depending on the species of increase) and cause predators or prey to distribute into new areas; such as predators moving into the area to prey upon the species of increase.


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Abiotic environment limit the distribution of species and biotic factors influence the structure and dynamics of aquatic biomes

  • Biotic and abiotic factors greatly influence the distribution of organisms of Earth. The combination of these factors make up the Earth’s many biomes.

  • Biomes are any of the world’s major ecosystems that was classified according to the predominant vegetation and characterized by adaptations of organisms to that particular environment.

  • Aquatic biomes account for the largest portion of the biosphere in terms of area.Two types: Freshwater Biomes                   Marine BiomesThe two are distinguished by their physical and chemical differences. EX: Freshwater Biomes have salt concentrations less then 1% whereas Marine Biomes generally average 3%.


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  • Marine Biomes environment limit the distribution of species- The oceans cover about 75% of the Earth’s surface- The evaporation of water from the oceans provides most of the plants rainfall- The ocean temperatures have a huge effect on world climate and wind patternsMarine algae and photosynthetic bacteria supply a big portion of the world’s oxygen and consume huge amounts of carbon dioxide.

  • Freshwater Biomes- The biomes are closely connected to the soils and other components of the of the terrestrial biomes through which they pass or are situated in.- The characteristics of the biomes are decided by the patterns and speed of water flow and climate in which the biome is in.


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  • Photic environment limit the distribution of species Zone-area where there is sufficient light for photosynthesis and where phytoplankton, zooplankton, and many fish species live

  • Aphotic Zone-area where little light penetrates and has very little life except for microorganisms and luminescent fishes

  • Benthic Zone-area at the bottom of all aquatic biomes where communities of organisms called benthos live and consume detritus which rains down from the productive surface of the photic zone

  • Abyssal Zone-area that is the deepest region of the ocean floor

  • Thermal energy from sunlight warms the surface waters to where ever the sunlight can reach, however the rest of the waters remain cold. A thermocline, which is a narrow stratum of rapid temperature change, separates the warm upper layer from the cold deeper waters.  


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Details of Effect DDT on environment limit the distribution of speciesAbiotic and Biotic Factors in Aquatic Biomes

  •   DDT can have a horrible effect on abiotic and biotic factors that influence the components of aquatic biomes. Aquatic biomes are all interconnecting because of evaporation, rainfall, currents, etc. Water that is in Mississippi can go through the water cycle and end up in India. This means that if there is DDT in the water supply, it can affect not only the area in which the water is in, but the areas in which the water may cycle too. All of Earth’s water supply could sooner or later be affected by DDT. Even if it’s just used in certain areas, water flows can take the water else where, slowly but surely contaminated the fish and animals of the area.            DDT mainly effects biotic factors since all living things take in nutrients. All organisms need water to survive, so when water is contaminated, other organisms suffer because they're ingesting the poison into their bodies. Even if the organisms don't directly use the contaminated water, they will still end up having DDT coursing thru their veins because of the food chain. 


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Population increase effects Biotic Factors, and the Ozone Hole effects Abiotic Factors.

  • Other species limit the distribution of a species. A population increase can cause an increase in negative interactions between species such as predation, parasitism, disease, or competition. An increase in population of a certain species may cause another species to have an inability to survive and reproduce.

  • This inability may also occur in the absence of another species on which a transplanted species depends. If the population of a species is too great, and limits the population of another required species or over hunts its prey, both species affected will decrease, even if not at the same time.

  • The hole in the ozone layer affects sunlight, an abiotic factor. This hole causes greater amounts of sunlight to pass through the atmosphere at stronger levels. Sunlight provides energy that drives nearly all ecosystems. The intensity and quality of sunlight limits the distribution of photosynthetic organisms. The hole in the ozone layer affects the intensity and quality of sunlight that photosynthetic organisms receive, which can be harmful to them. Many of these organisms may suffer population increases, and eventually, entire ecosystems may be affected.


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TERRESTRIAL BIOMES Hole effects

  • Terrestrial biomes are named for their physical or climatic factors and the predominant vegetation. Climographs are used to plot the temperature and precipitation of biomes which gives us evidence of the distribution of biomes. These biomes are characterized from the microorganisms, fungi and the animals. Typical features of terrestrial biomes may include their vertical stratification and the way the biomes grade into each other, also called as econtone.

  • Examples of terrestrial biomes include: desert, topical forest, tundra, and savanna


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Details of effect on DDT on Terrestrial Biomes Hole effects

  • The pesticide DDT can have a tremendous and negative effect onto Terrestrial biomes. If DDT enters the soil of terrestrial biomes  it can effect the species living there because it enters the food chain and in the fatty tissues of animals. Many of the organisms health will vary leading to many illnesses and deaths. DDT is passed from one organism to another. If an animal contains DDT and is used as prey the predator will then contain the pesticide, and so on and so forth. Thus leading to a chain. (Example of this is on birds.)  The population in the biomes will suffer as well as one of the factors that distinguishes one terrestrial biome to another. DDT can also effect Terrestrial biomes by effecting the plants. It can destroy the plant habitat which would lead to many long-lasting effects. One effect would be on the vertical stratification which varies on the shapes and sizing of plants.( a very important feature of the terrestrial biomes) Stratification also serves as a habitat for animals. If it is effected by DDT it will also effect the animals habitats.  In addition food would become more scarce, and the food living will be also contaminated from DDT. The animals eating that plant will take in the pesticide and thus the pesticide will be entered in the food chain. 


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Global Warming effects climate and terrestrial biomes. Hole effects

  • Temperature and rainfall are important to the distribution of biomes. When global warming interferes with the overall temperature of the earth, terrestrial biomes are directly effected. As temperature increases the variety of terrestrial biomes becomes more limited due to a smaller range of weather conditions. Terrestrial biomes that can tolerate warmer climates, such as deserts and tropical forests, will increase. Terrestrial biomes that exist in cooler climates, such as tundra and polar ice, will decrease over time.

  • Regions where biomes overlap may be affected as well, and cause one biome, that flourishes in a warmer climate, to dominate the area.

  • Currently, scientists have found that global warming has caused the polar ice caps to begin melting.


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