BT101 Handouts by VUBuddy

ECOLOGY, BIODIVERSITY & EVOLUTION - I (3+0) HANDOUTS

Lecture # 1

What is an ecosystem?

An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the system through photosynthesis and is incorporated into plant tissue. By feeding on plants and on one-another, animals play an important role in the movement of matter and energy through the system. They also influence the quantity of plant and microbial biomass present. By breaking down dead organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be readily used by plants and other microbes. Ecosystems are controlled by external and internal factors. External factors such as climate, parent material which forms the soil and topography, control the overall structure of an ecosystem but are not themselves influenced by the ecosystem. Unlike external factors, internal factors are controlled, for example, decomposition, root competition, shading, disturbance, succession, and the types of species present. Ecosystems are dynamic entities—they are subject to periodic disturbances and are in the process of recovering from some past disturbance. Ecosystems in similar environments that are located in different parts of the world can end up doing things very differently simply because they have different pools of species present. Internal factors not only control ecosystem processes but are also controlled by them and are often subject to feedback loops .Resource inputs are generally controlled by external processes like climate and parent material. Resource availability within the ecosystem is controlled by internal factors like decomposition, root competition or shading. Although humans operate within ecosystems, their cumulative effects are large enough to influence external factors like climate.

Lecture # 2

Living organisms can use many forms of energy, but not heat?

Organisms cannot convert heat to any of the other forms of energy. Thus, if organisms convert some chemical-bond or light energy to heat, the conversion is one-way; they cannot cycle that energy back into its original form. Living organisms must take in energy from their environment and convert it into to a form their cells can use. Organisms ingest large molecules, like carbohydrates, proteins, and fats, and convert them into smaller molecules like carbon dioxide and water. This process is called cellular respiration, a form of catabolism, and makes energy available for the cell to use. The energy released by cellular respiration is temporarily captured by the formation of adenosine triphosphate (ATP) within the cell. ATP is the principle form of stored energy used for cellular functions and is frequently referred to as the energy currency of the cell. The nutrients broken down through cellular respiration lose electrons throughout the process and are said to be oxidized. When oxygen is used to help drive the oxidation of nutrients the process is called aerobic respiration. Aerobic respiration is common among the eukaryotes, including humans, and takes place mostly within the mitochondria. Respiration occurs within the cytoplasm of prokaryotes. Several prokaryotes and a few eukaryotes use an inorganic molecule other than oxygen to drive the oxidation of their nutrients in a process called anaerobic respiration. Electron acceptors for anaerobic respiration include nitrate, sulfate, carbon dioxide, and several metal ions. The energy released during cellular respiration is then used in other biological processes. These processes build larger molecules that are essential to an organism’s survival, such as amino acids, DNA, and proteins. Because they synthesize new molecules, these processes are examples of anabolism.

Lecture # 3

Producers

Producers are organisms that make their own food; they are also known as autotrophs. They get energy from chemicals or the sun, and with the help of water, convert that energy into useable energy in the form of sugar, or food. The most common example of a producer are plants. Through a process called photosynthesis, green plants use sunlight and water and make a type of sugar called glucose. Green plants such as trees are found on land, but they can also exist underwater as long as there is enough sunlight. Although algae look like a plant, they're actually a special kind of single-celled organism called a protist. A protist cellular structure is different from a plant's, but it can still make its own food and, therefore, it is a producer. Algae and its relatives can be found in aquatic ecosystems. Surprisingly, single-celled bacteria can also be producers. Located deep below the ocean surface are areas that get little to no sunlight. Green plants can't survive there, since they are unable make food without sunlight. But, single-celled bacteria use a process to make food called chemosynthesis, which involves taking chemicals expelled from hydrothermal vents deep in the ocean and converting them into the same type of food that plants make. The food producers create food for themselves in order to grow and reproduce. However, plants also serve as food for the rest of the ecosystem, the consumers. Primary productivity is the productivity of the primary producers. Primary producers are that not only do they synthesize new organic matter by photosynthesis, but they also break down some of the organic matter to release energy by means of aerobic cellular respiration.

Examples of Trophic Level

Primary Producers

Primary producers, or “autotrophs”, are organisms that produce biomass from inorganic compounds. In general, these are photosynthesizing organisms such as plants or algae, which convert energy from the sun, using carbon dioxide and water, into glucose. This glucose is then stored within the plant as energy, and oxygen, which is released into the atmosphere. In terrestrial ecosystems, almost all of the primary production comes from vascular plants such as trees, ferns, and flowering plants. In marine ecosystems, algae and seaweed fill the role of primary production. There are also some deep-sea primary producers that perform oxidization of chemical inorganic compounds instead of using photosynthesis; these organisms are called” chemoautotrophs”.

Lecture # 4

Consumers

An organism that generally obtains food by feeding on other organisms or organic matter due to lack of the ability to manufacture own food from inorganic sources; a heterotroph. consumer pertains to any of the organisms in most trophic levels in a food chain, except for producers and decomposers. Consumers are also referred to as heterotrophs in contrast to autotrophs, which are the producers of the food chain. Consumers therefore include animals and heterotrophic bacteria and fungi. Plants that are carnivorous and therefore consume organic matter as well are regarded as both consumers and producers. In a food chain, the levels of consumers are primary consumers, secondary consumers, and tertiary consumers. Primary consumers are herbivores that feed on producers. Secondary consumers are consumers that feed on primary consumers and/or producers. Tertiary consumers are consumers that feed on secondary and primary consumers, as well as on producers. The trophic levels consist of the heterotrophs—the consumers. All the heterotrophs that feed directly on the primary producers are placed together in a trophic level called the herbivores.

Primary Consumers

Primary consumers are herbivores, that is, animals that are adapted to consuming and digesting plants and algae (autotrophs). Herbivores are generally split into two categories: grazers, such as cows, sheep and rabbits, whose diets consist at least 90% of grass, and browsers, such as deer and goats, whose diets consist at least 90% of tree leaves or twigs.