The Biosphere Chapter 3

Section 1: What is Ecology? Ecology – the scientific study of interactions among organisms and between organisms and their environment, or surroundings.

Biosphere – the combined portions of the planet in which all of the life exists, including land, water, and air, or atmosphere. It extends from about 8 km above Earth’s surface to 11 km below the ocean surface.

Levels of Organization To understand relationships within the biosphere, ecologists ask questions about events and organisms that range in complexity from a single individual to the entire biosphere.

Levels of Organization Species - a group of organisms so similar to one another that they can interbreed and produce fertile offspring. Populations – groups of individuals that belong to the same species and live in the same area. Communities – different populations that live together in a defined area. –These clams that live near an ocean vent constitute a population

Levels of Organization Ecosystem – a collection of all 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.

Ecological Methods Regardless of the tools they use, scientists conduct modern ecological research using three basic approaches: observing, experimenting, and modeling. All of these approaches rely on the application of scientific methods to guide ecological inquiry.

Section 2:Energy Flow Producers – organisms that make their own food (autotrophs). Autotrophs – plants, some algae and certain bacteria can capture energy from sunlight or chemicals and use that energy to produce food. Sunlight is the main energy source for life on Earth. Some types of organisms rely on the energy stored in inorganic chemical compounds.

Energy Flow – From the Sun Photosynthesis –the conversion of light energy into chemical energy which is stored within organic compounds.

Energy Flow – With NO Light! Chemosynthesis – when organisms use chemical energy to produce carbohydrates. Such as sulfur bacteria converting sulfur compounds into carbohydrates around thermal vents in the ocean. Ex: Chemosynthetic Bacteria Thermal vent

Consumers Heterotrophs – organisms that rely on other organisms for their energy and food supply; also known as consumers. Consumers include animals, bacteria & fungi

Energy Flow – Consumer Types Herbivores – animals that obtain energy by eating only plants. Ex: cows & caterpillars Carnivores – organisms that obtain energy by eating animals. Ex: snakes, dogs & owls Omnivores – organisms that obtain energy by eating both plants and animals. Ex: humans, bears & crows Detritivores – organisms that feed on plants and animal remains and dead matter (detritus). Ex: mites, earthworms & snails Decomposers – break down organic matter. Ex: bacteria & fungi

Feeding Relationships Energy flows through an ecosystem in one direction, from the sun or inorganic compounds to autotrophs (producers) and then to various heterotrophs (consumers). Food chain – a series of steps in which organisms transfer energy by eating and being eaten.

Tertiary and secondary consumers Secondary and primary consumers Primary consumers Producers (Plants, algae, phytoplankton) Detritivores (Prokaryotes, fungi, certain animals) Wastes and dead organisms Food Web – the feeding relationships among the various organisms in an ecosystem form a network of complex interactions; the interactions of all the food chains in an ecosystem.

TROPHIC LEVEL Quaternary consumers Tertiary consumers Carnivore HerbivoreZooplankton PlantPhytoplankton Secondary consumers Primary consumers Producers A TERRESTRIAL FOOD CHAINAN AQUATIC FOOD CHAIN Trophic Levels Each step in a food chain or food web is called a trophic level. Producers make up the first trophic level. Consumers make up the second, third, or higher trophic levels. Consumers depend on the trophic level below it for energy.

Ecological Pyramids An ecological pyramid is a diagram that shows the relative amounts of energy or matter contained within each trophic level in a food chain or food web. Energy Pyramid – shows the relative amount of energy available at each trophic level. Only about 10 % of the energy available within one trophic level is transferred to organisms at the next trophic level.

Ecological Pyramids Biomass – the total amount of living tissue within a given trophic level. Biomass is usually expressed in terms of grams of organic matter per unit area.

Section 3: Cycles of Matter Recycling in the Biosphere Unlike the one-way flow of energy, 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.

Solar heat Precipitation over the sea (283) Net movement of water vapor by wind (36) Flow of water from land to sea (36) Water vapor over the sea Oceans Evaporation from the sea (319) Evaporation and transpiration (59) Water vapor over the land Precipitation over the land (95) Surface water and groundwater Water Cycle

Evaporation – the process by which water changes from liquid form to an atmosphere gas. Transpiration – when water enters the atmosphere by evaporating from leaves of plants. Nutrient Cycles Nutrients – all the chemical substances that an organism needs to sustain life. Every living organism needs nutrients to build tissues and carry out essential life functions. Like water, nutrients are passed between organisms and the environment through biochemical cycles.

Carbon Cycle Carbon is a key ingredient of living tissues. Carbon and oxygen form carbon dioxide gas, an important component of the atmosphere. Four main types of processes move carbon through the carbon cycle. 1. Biological processes (photosynthesis, respiration, decomposition) take up and release carbon. 2. Geochemical processes (erosion, volcanic activity) release carbon dioxide. 3. Biogeochemical processes store carbon under ground as fossil fuels. 4. Human activities (mining, burning fossil fuels) release carbon dioxide into the atmosphere

Carbon Cycle CO 2 in atmosphere Cellular respiration Higher-level consumers Primary consumers Plants, algae, cyanobacteria Photosynthesis Wood and fossil fuels Detritivores (soil microbes and others) Detritus Decomposition Burning

Nitrogen Cycle Nitrogen is plentiful in the atmosphere as N 2 –But plants cannot use N 2 (This fact makes nitrogen fixing bacteria very important!) Nitrogen Fixation Various bacteria in soil (and legume root nodules) convert N 2 to nitrogen compounds that plants can use –Ammonium (NH 4 + ) and nitrate (NO 3 – ) Some bacteria break down organic matter and recycle nitrogen as ammonium or nitrate to plants Denitrification Other bacteria return N 2 to the atmosphere by converting nitrates into N 2

Nitrogen (N 2 ) in atmosphere Amino acids and proteins in plants and animals Assimilation by plants Denitrifying bacteria Nitrates (NO 3 – ) Nitrifying bacteria Detritus Detritivores Decomposition Ammonium (NH 4 + ) Nitrogen fixation Nitrogen-fixing bacteria in soil Nitrogen-fixing bacteria in root nodules of legumes Nitrogen fixation Nitrogen Cycle

Nutrient Limitation Primary productivity – the rate at which matter is created by producers. Limiting nutrients – single nutrient that either is scarce or cycles very slowly, limiting the growth of organisms in an ecosystem. Algal bloom – the result of runoff from heavily fertilized fields – the result is often immediate increase in the amount of algae and other producers.