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Ib Study Guide 1: Communities and Ecosystems

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    Biology IB Study Guide 1: Communities and Ecosystems 5. 1 Communities and Ecosystems (Core) 5. 1. 1Define species, habitat, population, community, ecosystem, and ecology. Species – A species is a group of organisms with similar characteristics, which can interbreed and produce viable, fertile offspring. Habitat – A habitat is the environment in which a species normally lives or the location of a living organism. Population – A population is a group of organisms of the same species, who live in the same area at the same time. Community – A community is a group of populations living together and interacting with each other in an area.

    Ecosystem – An ecosystem is a community and its abiotic environment. Ecology – Ecology is the study of relationships in ecosystems – both relationships between organisms and between organisms and their environment. 5. 1. 2Distinguish between autotroph and heterotroph. Autotrophs are organisms that synthesize their own organic molecules (food) from simple inorganic substances. More commonly known as producers, autotrophs make their own food. In most communities these producers create their own food through the process of photosynthesis. Meanwhile heterotrophs are organisms that obtain organic molecules (food) from other organisms.

    There are three different types of heterotrophs. The heterotrophs are represented by the consumers in a community, and can be found on the top of the food chain with the tertiary consumers. 5. 1. 3Distinguish between consumers, detrivores, and saprotrophs. There are three types of heterotrophs including consumers, detrivores, and saprotrophs. Consumers are organisms that ingest organic matter that is living or recently killed. Consumers are also split into three categories: primary, secondary, and tertiary consumers. Primary consumers directly ingest producers.

    Secondary consumers consume primary consumers as well as producers. Tertiary consumers are at the top of the food web and can consume any other consumers or producers. Detrivores ingest dead organic matter. And saprotrophs live on or in dead organic matter, secreting enzymes into it and absorbing the products of digestion. 5. 1. 4Describe what is meant by food chain, giving three examples, each with at least three linkages (four organisms). A food chain is visual representation of sequences of trophic relationships, where each member in the sequence feeds on the previous one.

    Trophic relationships are very important – where one population of organism feeds on another population. Example: Producer Primary consumer Secondary consumer Tertiary consumer 5. 1. 5Describe what is meant by a food web. A food web is a diagram of all the feeding relationships in a community. The arrows indicate the direction of flow of energy. 5. 1. 6 Define trophic level. Trophic level – The trophic level of an organism is its position in the food chain. Examples of this are producers, primary consumers, secondary consumers, and tertiary consumers. 5. . 7Deduce the trophic level of an organism in a food chain or food web. Photosynthetic organisms including plants, or all autotrophs, are producers in a food web. Primary consumers are organisms that eat only the producers. Secondary consumers then eat the primary consumers. And in turn the tertiary consumers eat the secondary consumers. 5. 1. 8 Construct a food web containing up to 10 organisms, using appropriate information. 5. 1. 9State that light is the initial energy source in all communities. In almost all communities the producers make organic matter through the process of photosynthesis.

    This making light is the initial energy source for the whole community. Producers convert light energy into the chemical energy of sugars and other organic compounds 5. 1. 10 Explain the energy flow in a food chain. Sunlight gives energy in organic matter to producers through the process of photosynthesis. When the primary consumers eat the producers, the energy is organic matter is transferred to them. About ten percent of the energy from the producers is transferred to the primary consumers. Then the secondary consumers eat the primary consumers and quire that energy though organic matter.

    About ten percent of the energy from the primary consumers is transferred to the secondary consumers and so on to the tertiary consumers. It is important to realize that energy is lost through the movement through each trophic level and this energy is released in heat. This energy release occurs through cellular respiration for use in the producer then lost as heat. In addition, as energy passes through the trophic levels not all the food is digested and then is lost in organic matter through feces. The feces as well as death of producers also gives energy to the detrivores and saprotrophs when they digest the producers. . 1. 11State that energy transformations are never 100% efficient. A large amount of the energy that is absorbed by an organism is released is cellular respiration. This energy that is ATP is then used in processes such as active transport or muscle contractions. These processes require energy transformations which are never 100% efficient. Some of this energy is converted into heat. 10-20% is a typical efficiency level. Most of the energy released by cell respiration is lost from the organism as heat. 5. 1. 12Explain the reasons for the shape of pyramids of energy.

    Pyramids of energy are always pyramid shaped because less energy flows through each successive trophic level. Energy is lost at each trophic level, through heat, so less remains available for the next level. In addition, mass is lost as well as energy, so the energy content per gram of the tissues of each successive trophic level is not lower. 5. 1. 13Explain that energy enters and leaves ecosystems, but nutrients must be recycled. Unlike nutrients, energy is not recycled. It is constantly being supplied from light to be used for photosynthesis by producers and then passed through all trophic levels.

    Energy can leave the ecosystem through the form of heat in saprotrophs and detrivores. This means that there needs to be a constant supply of energy entering the environment to ensure that the environment can transfer energy between trophic levels. Nutrients however, need to be recycled showing the interaction between living organisms and the abiotic environment they live in. Carbon, nitrogen, phosphorous, and all other necessary nutrients must be recycled because there is a limited supply of them. They are absorbed from the environment, used by living organisms and then returned to the environment.

    This is known as the carbon cycle. They are absorbed by the environment, used by living organisms, and then returned to the environment. 5. 1. 14State that saprotrophic bacteria and fungi (decomposers) recycle nutrients. Saprotrophic bacteria and fungi are essential in nutrient cycles because they release nutrients from dead organic matter and provide other organisms with these nutrients. They feed by secreting an enzyme into the dead organic matter which gradually breaks down the organic matter and the nutrients are released. The saprotrophs absorb the substances that they need from digested organic matter.

    G2 Ecosystems and Biomes (Option) G. 2. 1Define gross production, net production, and biomes. Gross production – the total amount of organic matter produced by plants in an ecosystem. Net production – the amount of gross production in an ecosystem remaining after subtracting the amount used by plants in respiration. Biomes – a certain type of ecosystem that develops in an area based on rainfall and temperature. G. 2. 2Calculate values for gross production and net production using the equation: gross production – respiration = net production. Gross production – Respiration = Net production

    Example: an old field community in Michigan Net production = 20. 79 x 10? kJ m?? year?? Plant respiration = 3 . 68 x 10? kJ m?? year?? Gross production = (20. 79 + 3. 68) x 10? kJ m?? year?? = 24. 47 x 10? kJ m?? year?? G. 2. 3Discuss the difficulties of classifying organisms into trophic levels. Classifying organisms into trophic levels can be difficult because many organisms can belong to two different trophic levels. An example of this would be certain plants, such as Euglena, that can photosynthesize and create its own food as a producer, however also use endocytosis to become a consumer.

    Other examples of this are chimpanzees, herring, and oysters. It can therefore be very difficult to classify organisms into trophic levels because they have such varied food sources. One solution that has been offered to solve this problem is to classify organisms based on their main food source only. G. 2. 4Explain the small biomass and low numbers or organisms in higher trophic levels. When using an energy pyramid, the amount of energy lost during each trophic level can be seen. In higher trophic levels, biomass can be lost as well. Respiration is a process in which both energy and biomass are lost.

    The total biomass available to members in the higher trophic levels is too small to support large numbers of organisms. This becomes important when the organisms need to be large and strong enough to over-power their prey. Therefore, higher trophic levels tend to have very low numbers of large organisms, resulting in a low total biomass per unit area. G. 2. 5Construct a pyramid of energy, given appropriate information. Pyramids begin from the bottom up, moving from producers, to primary consumers, to secondary consumers, and finally tertiary consumers.

    At each level usually only about 10% of the energy is passed up to the next level. Units of energy are measured in kJ m-2 yr-1. Trophic Level Energy in kJ m-2 yr-1 Secondary Consumer 49. 25 Primary Consumer 492. 5 Producers 4925 G. 2. 6Distinguish between primary and secondary succession, using an example of each. Ecological Succession is a series of changes in an ecosystem that was changed due to complex interactions between the community of living organisms and the abiotic environment.

    Primary succession starts in an environment where living organisms have not existed on previously. An example of this would be on a new island created by volcanic activity. Moss begins to grow, leading to small shrubs, then shrubs, then eventually trees. Secondary succession occurs in areas where an ecosystem is present but is replaced by other ecosystems, due to changes in conditions. An example of this would be an abandoned farmland that is becoming a forest or the land after a fire. Due to changes that are caused by ecological succession certain species may die out in the area, while other new species join the community.

    Overtime, this will eventually develop into a stable community, which is called the climax community. G. 2. 7Outline the changes in species diversity and production during primary succession. Firstly, because primary succession is creating life where there was none before, production and species diversity will increase during primary succession because it will have started as nothing. Because there are many changes that are caused by ecological succession, some species may die out of the ecosystem while other new ones may join the community.

    Overtime, the community will eventually work to develop into a stable community, which is called the climax community. This will cause production to increase greatly because the community will be working effectively, with each organism in a specific niche. G. 2. 8Explain the effects of living organisms on the abiotic environment, with reference to the changes occurring during primary succession. The amount of organic matter in the soil increases as organic matter released from plants and other organisms accumulate. In addition, organic matter binds minerals together, causing the soil to become deeper.

    Then organic matter content rises, resulting in improved soil structure. Also, the amount of water that can be retained and the water drainage rate increase. This allows for new organisms to develop faster and better in this environment. Then roots of larger plants reduce soil erosion, making it easier for roots to find firm group and grow. As mineral recycling increases, the soil can hold larger amounts of plants and minerals, resulting in higher amounts of minerals being held in the increasing biomass of the community. G. 2. Distinguish between biome and biosphere. Biomes are a certain type of ecosystem that develops in an area based on rainfall and temperature. Whereas the biosphere is a combination of all of the biomes in the world. All of the biomes and ecosystems on the Earth are part of one biosphere. G. 2. 10 Explain how rainfall and temperature affect the distribution of biomes. Rainfall and temperature affect the distribution of biomes because they determine the type of ecosystem in an area and what the distribution of biomes around the world is.

    The clinograph can show how rainfall and temperature can determine the type of biome. G. 2. 11 Outline the characteristics of six major biomes. There are six major biomes in the world. 1. Desert – A desert has a very low amount of precipitation. The days are usually warm to very hot, while the nights are cold. There is very little water available for organisms, so there are many organisms that store water or grow very quickly after rain. 2. Grassland – Grasslands usually have low amounts of precipitation. The summers are warm or hot, while the winters are cold.

    Grasslands are usually full of grass or other small herbs that can withstand grazing from animals. 3. Shrubland – Shrublands usually have cool, wet winters and hot, dry summers. There are often fires that occur naturally, causing secondary succession. They are usually full of drought-resistant shrubs in the area, often with evergreen foliage. 4. Temperate Deciduous Forest – Forests usually have moderate rainfall with warm summers and cool winters. They are usually dominated by trees that lose their leaves during the winter time.

    There are also many shrubs and herbs that occupy the area under the trees. 5. Tropical Rainforest – Rainforests typically have high amounts of precipitation and are hot throughout the entire year. There is a lot of diversity in both plant life and organisms. There are tall evergreen trees, along with smaller trees, shrubs, and herbs all in the same area. 6. Tundra – Tundras typically have very low temperatures with little precipitation, and it is usually in the form of snow. There are few small trees, along with herbs present. There are also mosses and lichens present in this biome.

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