Lecture 2 - Concepts of Ecology (Part I) PDF

Concepts of Ecology LECTURE 2 Topics Environmental factors affecting organisms Ecosystems ◦ Energy flow of the food web ◦ From ecosystems to biomes Organisms in Their Environment Ecology Ecology: the study of all processes influencing: ◦ The distribution and abundance of organisms ◦ Inter...

Concepts of Ecology LECTURE 2 Topics Environmental factors affecting organisms Ecosystems ◦ Energy flow of the food web ◦ From ecosystems to biomes Organisms in Their Environment Ecology Ecology: the study of all processes influencing: ◦ The distribution and abundance of organisms ◦ Interactions between living things and the environment  The hierarchy of life Life consists of a hierarchy of complex systems © 2017 Pearson Education, Inc Species Species: a group of individuals that share certain characteristics ◦ But are distinct from other groups Species are grouped into genera ◦ Which are grouped into families, orders, classes, phyla, kingdoms, and domains The official species name is Latin and has two parts ◦ The genus name and species descriptive term Same species? Same species? Species All members of a species can interbreed and produce fertile offspring ◦ Members of different species generally do not breed But what about organisms that do not mate to produce offspring? (Eg. Bacteria) ◦ Scientists use other classification methods (eg. Similarities in proteins produced) New species arise due to evolution ◦ Species classifications are changed to reflect this Two species Similarity between two species: the eastern meadowlark (left) and western meadowlark (right) Population In the hierarchy of life, a population is a group of interacting individuals of a particular species. Population: a group of individuals of the same species that live in the same area. ◦ Only those individuals of a species in an area (e.g., gray wolves in Yellowstone National Park) ◦ A species would be all inclusive (e.g., all the gray wolves in the world) Community Species in a community depend on each other ◦ The plant community supports and limits animals Populations of different species within a biotic community constantly interact ◦ With each other and with the abiotic environment The variability or stability in the species composition of a community caused by biotic and abiotic factors. Abiotic and Biotic Factors Biotic factors relate to all the living things in the ecosystem. Biotic factors refer to all living organisms from animals and humans, to plants, fungi, and bacteria. Abiotic factors refer to all the non-living, i.e. chemical and physical factors present in the atmosphere, hydrosphere, and lithosphere. Sunlight, air, precipitation, minerals, and soil are some examples of abiotic factors. Ecosystems Ecosystem: an interactive complex of communities and their abiotic environment ◦ Forests, grasslands, wetlands, coral reefs, humans They lack distinct boundaries and are not isolated ◦ Species can occupy multiple ecosystems and move between them Biome and Biosphere Biome: a large area with the same climate and vegetation ◦ Can be predicted by rainfall and temperature ◦ There are no sharp boundaries between biomes Aquatic biomes are determined by depth, salinity, and permanence of water Biosphere: the huge system of all living things Environmental factors affect organisms Physical, chemical, and biological factors (biotic or abiotic) affecting organism survival Condition: a factor that varies in space and time ◦ not used up (temperature, wind, pH, salinity) Resource: a factor consumed by organisms ◦ Water, nutrients, light, oxygen, food, space A factor can be both a condition and resource ◦ Plants use water as a resource, but ocean water is a condition for many fish, algae, and penguins Survival = Organisms happily live and will be able to reproduce.  Survival Curve Range of tolerance: the entire span allowing any growth at all Limits of tolerance: the high and low ends of the range of tolerance Zones of stress: between the optimal range and high or low limit of tolerance © 2017 Pearson Education, Inc. fundamental biological principle Every species has an optimum range, zones of stress, and limits of tolerance for every abiotic factor ◦ These characteristics vary among species ◦ Some species have a broad range of tolerance ◦ Other species have a narrower range The range of tolerance for a factor affects an organism’s growth, health, survival, reproduction The population density of a species is greatest where all conditions are optimal Habitat vs. niche Habitat: place where a species is adapted to live ◦ It is defined by the plant community and physical environment ◦ Microhabitat: puddles, rocks, holes in tree trunks Ecological niche: the sum of all conditions and resources under which a species can live ◦ What the animal eats, where it feeds and lives, how it responds to abiotic factors Species coexist in a habitat ◦ But have separate niches ◦ Reducing competition by using different resources Quick activity: Search for examples of organisms living in the same habitat but having different ecological niche  Organisms need food in order to survive Hence, it is important for food chains and food web to exist in an ecosystem. We see organisms being eaten / organisms eat another organism in a food web. Apart from ‘food’ flowing from one level to another, energy is often used as the terminology to describe the flow from one organism to another.  Energy flow of the food web Food chains ◦ A sequence of organisms, each of which serves as a nutritional source for the next (big fish eat little fish) Food webs ◦ A complex network of interconnected food chains Pyramid of energy flow ◦ Energy flow through various trophic levels Energy flow of the food web Plant photosynthesis produces organic molecules Energy is passed through the food chain ◦ Herbivores eat plants and are eaten by predators ◦ Organisms obtain energy from cells through cellular respiration Organisms are linked by food chains that describe where energy and nutrients go ◦ Energy moves “up” through the food chain ◦ Most energy is lost going to higher trophic levels ◦ Food chains are interconnected into food webs  A meadow food web Food chains are interconnected into more complex food webs © 2017 Pearson Education, Inc. Trophic levels Autotrophs (producers): produce their own organic material from inorganic molecules ◦ Plants, photosynthetic microorganisms, and bacteria Heterotrophs: organisms that must consume organic material for energy ◦ Consumers: eat living prey ◦ Decomposers: break down dead organic material Organisms produce food, pass it along the food chain, and return materials to the environment Producers Most terrestrial producers are green plants photoautotrophs ◦ Chlorophyll: a green pigment that captures light energy to convert CO2 and H2O to organic matter Range from microscopic bacteria to gigantic trees ◦ Every major ecosystem has producers ◦ Oceans have vast numbers of microscopic producers Chemosynthesis: some bacteria use energy in inorganic chemicals ◦ To form organic matter from CO2 and H2O Consumers Consumers range in size from plankton to blue whales They are categorized according to their food source ◦ First-order consumers (herbivores): eat producers ◦ Second-order consumers: eat primary consumers ◦ Third (tertiary), fourth (quaternary), or higher levels Animals can occupy multiple levels ◦ Depending on the food they eat Carnivores: second-order or higher-order meat eaters Omnivores: feed on both plants and animals Trophic levels in a grassland © 2017 Pearson Education, Inc. Trophic level 4 A typical food chain consists of about 4 to 5 trophic levels. Trophic level 3 Why? Why can’t a food chain consists of Trophic 7 to 8 trophic levels? level 2 Trophic level 1 It’s all related to energy transfer When an organism consumes the prey, energy is transferred from trophic level to another. However, this transfer is not efficient. Only about 10% of energy from the prey is transferred to the next trophic level. This 10% energy transfer is applicable to every trophic level. Only 10% of energy can be transferred. Hence, at the 5th trophic level, very little energy is remaining. There will not be sufficient energy left for the 6th trophic level. Conclusion: The number of trophic levels in a food chain is dependent on the amount of energy available.  Why is there only a 10% of energy transfer? What happens to the rest of the energy? Remember, energy cannot be created nor destroyed. If there is only a 10% of energy transfer from one organism to another, it means that 90% of the energy must have been lost somewhere! Reasons for energy lost: 1) At every trophic level, a huge amount of energy is released as heat when respiration is being carried out. 2) Some parts of the organism when eaten cannot be digested to release as energy. Instead, it becomes part of faeces to be excreted by the consumer. Eg., when human beings consume plants, cellulose (part of the plant cell wall) cannot be digested and end up as part of our faeces. Some of the energy is stored in your faeces and gets excreted! 3) Not all organisms in a trophic level get eaten up. Some organisms die and will be left to be decomposed in the soil. Decomposers Detritus: (Actually means thrash). Refers to dead plant material (leaves, etc.), fecal wastes, and dead bodies ◦ Most ecosystem energy goes through this food web Detritus is organic and high in potential energy for: ◦ Scavengers (vultures): decomposers that break down large pieces of matter ◦ Detritus feeders (earthworms): decomposers that eat partly decomposed matter ◦ Chemical decomposers (fungi and bacteria): break down molecule-sized matter Well, fortunately, we still have the decomposers  Decomposers feed on the excreted faeces and uneaten dead organisms. They will release the energy from faeces and dead organisms back to the environment as heat energy. The decomposers also help to recycle the nutrients from the dead organisms and faeces back to the soil (to be absorbed and reused by the plants again)  Examples of scavengers Hyenas Jackals  A detritus food web Decomposers break down dead organic matter and are the major source of nutrients in most ecosystems © 2017 Pearson Education, Inc. All the energy will be returned to the environment eventually! Different ecosystems have different amount of energy flowing. Why?? This has something to do with the productivity of an ecosystem Productivity - The effectiveness of the producers in a community to convert sunlight energy to become organic forms of energy. (Rate of energy added to the bodies of producers in the form of biomass) The higher the productivity, the more producers there will be. Imagine the productivity of a cookie baker: Productivity – how effective is he in converting raw ingredients into cookies  Productivity (Gross Primary Productivity) Cookies for sale! (Net Primary Productivity) Keep some for myself… GPP & NPP Gross primary productivity = The rate of solar energy being captured in sugar molecules during photosynthesis. Net primary productivity = GPP – rate of energy loss for respiration NPP = the amount of energy available for consumers at the next trophic level. Brainstorm: What factors could increase or decrease GPP and hence NPP? Answer: Temperature / humidity / amount of nutrients in soil / Amount of sunlight etc.  Productivity For plant’s own energy Available to next trophic requirement (respiration, level – Net Primary growth etc) Productivity An ecosystem with a high productivity Often has high biodiversity. Biodiversity refers to the variety and types of all life forms on earth. This includes microorganisms. Biodiversity has a lot of ecological and economical significance. The richness in species provide human beings with housing, fuel, nutrients, medicinal purposes etc. Ecological pyramids Ecologists compare trophic levels by determining the number of organisms, biomass, or relative energy at each level, which are presented graphically as ecological pyramids. Types of pyramids: Pyramid of energy Pyramid of biomass Pyramid of numbers  A biomass pyramid Only about 10% of the energy contained in one trophic level is incorporated into the bodies of the next trophic level © 2017 Pearson Education, Inc. Task: Name one ecosystem that has a very high productivity. Explain why Name one ecosystem that has a low productivity. Explain why 57 Productivity of different ecosystems © 2017 Pearson Education, Inc.