Chapter 3 The Biosphere Ecologists study the Biosphere

Chapter 3: The Biosphere Ecologists study the Biosphere…

What is Ecology? n n Ecology is the scientific study of interactions among organisms and between organisms and their own environment, or surroundings. Ecology comes from the Greek word ”oikos” meaning house. It is also the root word for economy.

Nature’s houses come in many sizes-from single cells to entire planets. n n Biosphere-the combined portions of the planet in which all life exists, including land, water and air, or atmosphere. It is the largest of nature’s houses. Facts about the biosphere: 1. It extends from about 8 km above Earth’s surface to as far as 11 km below the surface of the ocean. 2. Interactions within the biosphere produce a web of interdependence between organisms and the environment in which they live.

Levels of Organization: n n n Species-a group of organisms so similar to one another that they can breed and produce fertile offspring. Populations-groups of individuals that belong to the same species and live in the same area. Communities-assemblages of different populations that live together in a defined area. Ecosystem-a collection of all the organisms that live in a particular place, together with their nonliving, or physical, environment. Biome-a group of ecosystems that have the same climate and similar dominant communities.

Work of Ecologists… n n Individual ecologists study all of these, except for the biome, which is so large that a group or team of ecologists examine it together. The highest level of organization studied by ecologists is the biosphere. Ecologists utilize a wide range of tools and techniques to study the living world such as binoculars, field guides, DNA studies, radio tags, or other data. Ecological research is conducted via three basic approaches: observing, experimenting, modeling.

Energy Flow n n Sunlight is the main source of energy for life on Earth. Some types of organisms may depend on energy stored in inorganic chemical compounds. Autotrophs-organisms that utilize energy from the environment to fuel the assembly of simple inorganic compounds into complex organic molecules. Ex. Plants, some algae, and certain bacteria. Producers-make their own food and are essential to the flow of energy through the biosphere.

A producer may capture energy from sunlight, or capture chemical energy. n n Photosynthesis-a process in which autotrophs utilize light energy to power chemical reactions that convert carbon dioxide and water into oxygen and sugar. Chemosynthesis-a process in which organisms utilize chemical energy to produce carbohydrates.

Who are the main autotrophs on land? n Plants

Who are the main autotrophs in ecosystems and in the sunlit upper layers of the ocean? n algae

Heterotrophs are organisms that rely on other organisms for their food supply. n n n Types of heterotrophs: Herbivores-obtain energy by eating only plants. Carnivores-eat other animals. Omnivores-eat both plants and animals. Detrivores-feed on plant and animal remains and other dead matter collectivley called detritus. Decomposers-break down organic matter.

Examples of heterotrophs n n n Herbivores-cows, deer, caterpillars Carnivores-snakes, dogs, owls Omnivores-humans, bears Detrivores-mites, snails, earthworms, crabs Decomposers-bacteria, fungi

What happens to the energy in an ecosystem when one organism consumes another? n n Energy flows through an ecosystem in one direction, from the sun or inorganic compounds to autotrophs (producers) and then to various heterotrophs (consumers). The energy stored by producers can be passed through an ecosystem along a food chain.

Energy Use n Food chain-a series of steps in which organisms transfer energy by eating and being eaten. n FOOD CHAIN (just one path of energy)

Food Web-develops when the feeding relationships among the various organisms in an ecosystem form a network of complex interactions. n FOOD WEB (everything is connected!)

Trophic level-each stepin a food chain or a food web. n n n Producers comprise the first trophic level. Consumers make up the second, third, or higher trophic levels. Ecological pyramid-a diagram portraying the relative amounts of energy or matter contained within each trophic level in a food chain or food web.

Three types of ecological pyramids: n n n Energy pyramid Biomass pyramid Pyramid of numbers *Only part of the energy that is stored in one trophic level is passed on to the next level. Only about 10% of the energy is available within one trophic level. Biomass-the total amount of living tissue within a given trophic level.

Cycles of Matter n n n Read paragraph #1 on page 74. Matter is recycled within and between ecosystems. Biogeochemical cycle-process in which elements, chemical compounds, and other forms of matter are passed from one organism to another and from one part of the biosphere to another. Matter can cycle through the biosphere because of the law of conservation of matter. Also read paragraph #3 on page 74.

Cycles in the biological systems n n n The Water Cycle: Water moves between the ocean, atmosphere, and land. Water is cycled in the following manner: Evaporation-process where water changes from liquid to form an atmospheric gas. (Water may also enter the atmosphere by evaporating from the leaves of plants in the process of transpiration). Condensation-clouds. Precipitation-hail, rain, sleet, or snow.

Nutrient Cycles n n Nutrients-all the chemicals that an organism needs to sustain life. How do primary producers obtain nutrients? Primary producers such as plants obtain nutrients in simple inorganic forms from their environment. How do consumers obtain nutrients? Consumers obtain nutrients via consuming other organisms. Carbon, nitrogen, and phosphorus are all part of this nutrient cycle.

The Carbon Cycle n n The recycling of carbon dioxide, CO 2. Carbon dioxide is taken in by plants during photosynthesis and given off by both plants and animals during respiration.

Four main types of processes that move carbon through the carbon cycle: n n 1. Biological processes (e. g. photosynthesis and respiration). 2. Geochemical processes (e. g. erosion and volcanoes). 3. Mixed biogeochemical processes (e. g. burial and decomposition of dead organisms and their conversion under pressure to coal and petroleum). 4. Human activities (e. g. releasing carbon dioxide into the atmosphere and burning forests).

The Nitrogen Cycle n n n All organisms require nitrogen to make amino acids, which are utilized to build proteins. Nitrogen gas comprises 78% of Earth’s atmosphere. Only certain forms of bacteria can directly utilize nitrogen. Nitrogen fixation-process where nitrogen gas is converted into ammonia in order for producers to be able to utilize the products of nitrogen (nitrites and nitrates). Denitrification-process of converting nitrates into nitrogen gas; releases nitrogen into the atmosphere once again. Consumers eat producers and reuse the nitrogen to make their own proteins. Once an organism dies. Decomposers return nitrogen to the soil as ammonia.

The Phosphorus Cycle n Phosphorus forms part of the nucleic acids, DNA and RNA. It is not a part of the biosphere and does not enter the atmosphere. Here, phosphorus is recycled. Organic phosphate moves through the food web, from producers to consumers.

Summary

The Nitrogen Cycle

Summary n n n Matter is recycled through producers, consumers, and decomposers. Energy is passed on and exchanged up the food chain. Nutrient limitation: Primary productivity-the rate at which organic matter is created by producers. A factor controlling the primary productivity of an ecosystem is the amount of available nutrients. Limiting nutrient-substance that is scarce or cycles slowly. Because of limiting nutrients, farmers apply fertilizers to their crops in order to boost productivity. Fertilizers contain three important nutrients: nitrogen, phosphorus, and potassium. In the ocean, nitrogen is often the limiting nutrient. Algal bloom-result of an aquatic system receiving a large input of a limiting nutrient when an immediate increase in the amount of algae and other producers occurs.