Chapter 7 Nutrient and Energy Relations Updated (6) copy.pptx
Transcript
Chapter 7 Energy and Nutrient Relations 7.1 Obtaining Energy • Organisms use one of the three main sources of energy; light, organic molecules, or inorganic molecules. • Classification of the organisms by how they obtain energy…(trophic (feeding) biology) • 1. Autotrophs (self-feeders) • a. Photo...
Chapter 7 Energy and Nutrient Relations 7.1 Obtaining Energy • Organisms use one of the three main sources of energy; light, organic molecules, or inorganic molecules. • Classification of the organisms by how they obtain energy…(trophic (feeding) biology) • 1. Autotrophs (self-feeders) • a. Photosynthetic autotrophs (plants) use carbon dioxide (co2) as a source of carbon and light as a source of energy. • b. Chemosynthetic ( bacteria) autotrophs us inorganic molecules as a source of carbon and energy. Obtaining Energy • 2. Heterotrophs: are organisms that use organic molecules both as a source of carbon and source of energy. E.g. bacteria, fungi, protists, animals, and parasitic plants. 7.2 Photosynthesis sunlight Carbon dioxide + water absorbed by chlorophyll glucose + oxygen 7.3 Respiration • Respiration is the exact opposite of photosynthesis! glucose + oxygen → carbon dioxide + water + Energy C6H12O6 +6O2 → 6CO2 + 6H2O + energy Photosynthesis and Respiration together make the Carbon cycle. 7.4 The Solar-Powered Biosphere • Longer wavelength, such as, infrared light, carry less energy than shorter wavelength, such as visible and ultraviolet light. • Visible light that we can see is called also photosynthetically Active Radiation (PAR) • • With wavelengths between 400 and 700 nm carries sufficient energy to drive the light-dependent reactions of photosynthesis but not much as to destroy organic molecules. • • • PAR makes up about 45% of the total energy content of the solar spectrum at sea level, while infrared light accounts for about 53% and UV light for the remainder (2%). Electromagnetic Spectrum 7.5 Measuring PAR… • Ecologists quantify PAR as a photon flux density • and it is the number of photons striking a square meter surface each second. • • The number of photons is expressed as micromoles (µmol). A photon flux density about 4.6 µmol / m2/s this equals a light intensity of about 1 watt per square meter. • Light changes in quantity and quality with, 1. Seasons 2. Weather 3. Time of the day 4. also, landscapes, water, and even organisms 7.6 Using Organic Molecules • There are 4 major categories: • 1. Herbivores; organisms that eat plants. • 2. Carnivores, organisms that mainly eat animals. • 3. Decomposers: Break down the dead organisms through decomposition (Fungi and Bacteria). 4. Detritivores, organisms that feed on decaying nonliving organic matter (remains of animals & plants). Examples: worms, millipedes, woodlice, dung flies, and slugs 7.7 Chemical Composition and Nutrient Requirements • Biologists have found that the chemical composition of organisms is very similar. Just 5 elements C, O, H, N, and P make up 93 to 97% of the biomass of plants, animals, fungi, and bacteria. • Among these four groups, … • plants are the most distinctive chemically. Plant tissues contain lower concentration of P and N. Nitrogen Content of Plants • The nitrogen content of plant tissues about 2%,while in fungi, animals, and bacteria about 5 to 10%. • Ecologist express the relative nitrogen content of whole organisms or tissues as the ratio of carbon to nitrogen (C:N). • A high C:N ratio indicates low nitrogen content. The C:N ratio of plants average about 25:1> than C:N ratio of animals, fungi, and bacteria which average 5:1 to 10:1. 7.8 Chemical Defenses • When ecologists talk about plant chemical defenses, however, they are generally referring to two other classes of chemicals, toxins and digestion-reducing substances. • Toxins: are chemicals that kill, impair, or repel most would be consumers. • Digestion-reducing substances: are generally phenolic compounds such as tannins that bind to plant proteins, inhibiting their breakdown by enzymes. • Chemists notice that more tropical plants contain toxic alkaloids than do temperate. Chemical Defenses Chemical Defenses • Despite these higher levels of chemical defense, Herbivores appear to remove approximately 11 to 48% of leaf biomass in tropical forests, while in temperate forests they remove about 7%. • So… • These higher levels of herbivore attack on tropical plants suggest that natural selection for chemical defense is more intense in tropical plant populations. 7.9 Energy Limitation • The rate at which organisms can take in energy is limited • Imagine that we have free access to a candy , ice-cream factory, what might we do?? Energy Limitation • But even if we were given a chance to do this, our rate of intake would be limited, not by supply but by the rate at which we could process what we ate. (Size of Stomach). • If organisms are not limited by the availability of energy in the environment, their energy intake is limited by internal constraints 7.10 Photon Flux and Photosynthetic Response Curves: • Photosynthetic potential of plants in environment: • If the environments have abundant nutrients and water, normal conc of oxygen and carbon, ideal temp and high humidity……………………….????? Less water from the plant evaporates and the rate of photosynthesis increases. • If you gradually increase the intensity of light shining on plants growing under these conditions, that (increase the photon flux density) so the plant’s rates of photosynthesis gradually increase and then level off. Photon Flux and Photosynthetic Response Curves: • At low light intensities, photosynthesis increases linearly with photon flux density. • At intermediate light intensities, photosynthetic rate rises more slowly. • Finally, at high light intensity, but well below that of sunlight, photosynthesis level off. • Pmax is measured as amount of co2(µmol)/m2/second Photon Flux and Photosynthetic Response Curves: • Let’s examine the structure of a theoretical photosynthetic response curve, • Differences in photosynthetic curves have been used to divide plants into sun and shade species. • The response curves of plant from shady habitats suggest selection for efficiency at low light intensities. • The photosynthetic rate of shade plants levels off at lower light intensities. • However, at very low light intensities, shade plants usually have higher photosynthetic rates than sun plants. 7.11 Food Density and Animal Functional Response • Functional responses is a Term that describes the relationship between an individual’s rate of consumption and food density. • Type 1: Functional response is a linear increase in consumption rate as food densities rise, until reaching a maximum consumption rate. • A "true" type I functional response is possible when handling time is equal to zero. Example: Animal that feeds on a small prey requires little or no time to process their food (filter-feeding aquatic animal that feeds on small prey). Examples: Whales and Sharks. Type 1 Functional Response Food Density and Animal Functional Response: • Type 2 Functional Response: Feeding rate at first rises linearly at low food density (depend on the time required to find the food), rises more slowly at intermediate food density (searching and handling the food), for example: 1. Removing distasteful scent glands from prey 2. chasing down elusive prey. and then levels off at high densities, an animal does not have to search for food at all and feeding rate is determined entirely by how fast the animal can handle its food. Example: Wolves feeding on deer. Food Density and Animal Functional Response: • In Type 111, The number of prey caught per predator per unit time increases slowly at low prey densities, but fast at intermediate densities before levelling off at high densities, producing an S-shaped curve. • The S shape of this curve is attributed to a behavioral characteristic of predators such as prey-switching and learning time. Examples: Birds and Shrew feeding on sawflies. Shrew Feeding on sawflies. Food Density and Animal Functional Response: • Why does feeding rate increase slowly at low densities? • At low density, food organisms may be better protected from predator because they occupy relatively protected habitats or safe site and also animals often ignore uncommon foods and focus most on more abundant foods. • Animals may require some learning to exploit food and develop their searching and handling skills
