Biology Exam #2 - Energy Flow and Trophic Structure

Trophic Structure: Consumers are..

Consumers are Heterotrophs, organisms that feed on other organisms to obtain energy for maintenance, growth, and reproduction. consumers include: 1. herbivores - primary consumers 2. carnivores - secondary consumers, or tertiary or quaternary and/or Primary carnivores or secondary carnivores, etc. primary consumers (herbivores) - 1st level, or secondary tertiary of quaternary, refer to herbivores (plant eaters) carnivores (meat) omnivores (everything). can classify herbivores more specifically, same with carnivore and omnivores. its producers vs. consumers

Trophic Structure: Decomposers (Detritivores)

Decomposers (Detritivores) - get energy from consuming dead organisms or their wastes. individuals eating dead primary producers and consumers or their waste products, cycling nutrients back into soil/water so they can be used again by primary producers.

define Food Web

Food web (SEE FIGURE 54.5 FOR EXAMPLE) 1. compact way of summarizing energy flow and documenting the complex trophic interactions that occur in communities. 2. food webs are highly interwoven. there are typically several links through each level, and maybe several links through each individual. 3. food webs cannot be understood solely on the basis of their direct interactions. that is to say, a food web is not simply a collection of food chains. i.e. a predator may reduce competition between prey species by keeping numbers low (as in keystone species) i.e. prey may impact predator/predator competition Food web for African Savanna designed so has decomposers on bottom, then acacia tree and other grasses being food itesm for variety of species and those species food items for other species. web - multiple items are food for multiple animals, and multiple animals are predators for multiple food items. grass being eaten by termites, zebras, wildebeast, etc. see relationships within ecosystem better with food web. food web is not a collection of food chains (how you construct it) it needs to be considered interpretation is different from what you would get from a food chian. see multiple things - you don't get that from food chain. food web = better apreciation of how predators/prey affect each other - especially because they effect multiples on multiples

What is NPP? How much of NPP is harvested by animals?

NPP - Net Primary Productivity - is GPP minus that energy used for respiration. in other words, NPP is the amount of matter in plants that is plant material and that may be available to herbivores. depending on the ecosystem, somewhere between 10 and 70% of NPP is harvested by animals.

Trophic Structure: define abiotic environment

abiotic environment - includes sunlight, soil, climate, temperatures, local weather conditions, water, and nutrients. keep in mind, nutrients refers to elements and molecules that an organism takes out of the environment to use. for plants, this refers to the elements and small molecules in the soil and the air (and sometimes directly from other organisms) (e.g. potassium, zinc, ammonium, etc.). remember, plants do not get carbon out of the soil. they get it from the air in the form of CO2. being consumers, we often confuse nutrients with food. But plants create their own food. Consumers get their nutrients from plants and other organisms. ecosystems is a community + abiotic factors that surround a particular community. community interacting + abiotic factors - sunlight, geology, temperature - these are abiotic. look at ecosystems in level by level way for this.

energy flow specifics - what do the previously mentioned energy possibilities all require?

all of these energy options require the functioning of cells. and the cells use carbohydrate to function. this is respiration, and is the opposite of photosynthesis: C6H12O6 + 602 + 6H20 --> 6CO2 + 12H20 + ENERGY notice that CO2 is given off during cellular respiration

How much of a plant's energy usage is in what form?

approximately 50% of a plant's energy usage is in the form of cellular respiration only (the remainder goes to storage and building bulk plant matter). that means that energy that is not used for respiration becomes available energy for herbivores. (keep in mind that not all plant matter is available to herbivores due to various defense mechanisms and availability).

Trophic Structure: What are the two ways in which created chemical energy is used?

created chemical energy is used for: 1. maintenance and respiratory costs 2. growth and reproduction

what is ecosystem science mainly concerned with? 2 things.

ecosystem science is largely concerned with: 1. energy flow 2. cycling of matter

define ecosystem

ecosystems are communities plus the abiotic conditions that surround them.

what starts energy flow?

energy flow starts with solar radiation striking a part of earth. some of it is reflected back into the atmosphere and space. some is absorbed by organisms, soil, water, etc., increasing their kinetic energy and raising their temperature. temperature affects the rate of biochemical reactions within an ecosystem. some of the incoming sunlight is absorbed by chlorophyll in plants.

Energy flow specifics - Where is energy stored? What happens to it?

energy is stored in the chemical bonds of carbohydrate. what happens to it? 1. it may be stored as starch 2. it may be used for growth of plant material 3. it may be used for reproduction 4. it may be used for plant maintenance

What happens every time a cell respires? What is the rate of efficiency, is it the same for all cells?

every time a cell respires, energy is released from the bonds of the carbohydrates and is used to drive cellular function. because this process is not 100% efficient, some of the energy is lost from the system and is not used by the organism nor by the others in the community. this is true for all cells.

define Food Chain (FIGURE 54.2!)

food chain: 1. connects the trophic levels in an ecosystem and describes how energy flows between trophic levels.essentially a food chain is a list of who eats whom in an ecosystem. 2. at higher levels, many food chains merge. also, all food chains end up going into the decomposer food chain eventually. 3. most organisms eat more than one type of food, and many are represented at different trophic levels in different food chains. so the idea of a food chain is a little over-simplyfying. food chain - graph of whom eats whom, how does each level get energy. written specific to particular environments and particular communities 54.2 - DECOMPOSER FOOD CHAIN have primary producer green leaf die turn brown fall off and start getting decomposed by bacteria and archae - those bacteria and archae then eaten by consumer, probably herbivore. so able to label each trophic level as primary or secondary consumer, and primary secondary decomposer as well. could say robin is primary carnivore, bc earth worm first animal introduced. secondary carnivore - eats robin compare then to grazing food chain - starts with green leaf, primary producers, then cricket, crickets love eating green leaves, call them primary consumer, therefore cricket is herbivore, robin is secondary consumer in this one, then tertiary is what eats robin. often have overlap in players from one food chain to other - robin involved in two different food chiains. you get an awful lot of overlap. his isTREMENDOUS OVER SIMPLIFICATION - bc it is, and end up with overlaps, often talk about food webs rather than food chains.

describe ecological efficiency

given that we know a certain amount of energy is lost with cellular function, we can then describe how efficiently energy moves from one trophic level to the next. we refer to this as ECOLOGICAL EFFICIENCY. ecological efficiency is the percent energy transferred between trophic levels

Energy Flow Specifics - how much of the sunlight striking the earth is captured by plants?

on average, less than 1% of sunlight striking earth is captured by plants

Energy Flow Specifics - where do plants get CO2 from? what do they convert it to?

plants take in CO2 from the atmosphere and convert it (and water) to sugar by photosynthesis.

general overview of energy flow start to finish

plants use sunlight energy to convert carbon dioxide and water into carbohydrate, which provides herbivores with a useable form of energy. herbivores take in these molecules and transform them. the new molecules can then be used by carnivores. additionally, all organisms defecate, shed skin, hair and/or feathers, and all eventually die. the molecules of these non-living organic bits provide energy for use by decomposers, who break down the molecules and return nutrients to the soil. these nutrients can be then taken up by plants so the process can start over again.

Trophic Structure: define primary producers

primary producers - most are plants, bacteria, and algae (autotrophs) that produce their own food through photosynthesis. a few are bacteria that convert inorganic compounds to food in extreme environments. primary producers are largely plants, but some bacteria will convert inorganic matter into energy sources. plants are autotrophs, create their own food through the process of photosynthesis convert sunlight and CO2 to produce carbohydrates

Pyramid of Productivity

pyramid of productivity shows that productivity (total net biomass production) is highest at the bottom, or first, trophic level, and decrease dramatically as you move up through the higher trophic levels

What is the typical ecological efficiency?

studies indicate the typical ecological efficiency is somewhere between 10-20%. The majority of research reports that most values are closer to 10% than 20%

Energy Flow Specifics - note the chemical formula for photosynthesis, what is significant about carbon?

the process of photosynthesis is: 12H20 + 6CO2 + SOLAR ENERGY --> C6H1206 + 6O2 + 6H20 (cross out h12o6+6) notice the uptake of carbon in the form of CO2. this is the only way in which plants get carbon. they do not take up carbon from the soil.

Energy flow specifics - what is GPP?

the total amount of carbohydrates created by plants is referred to as Gross Primary Production (GPP)

define Trophic Level

trophic level - (figure 54.2) - organisms that obtain their energy from the same type of source are said to be in the same trophic level. for most part, food represents energy. talk about transfer of food as pertains across different trophic levels. trophic level = group of organisms that gets its energy in same style from same place i.e. plants/autotrophs - from sun, same trophic level herbivores - same trophic level secondary consumers - get energy from eating herbivores, same trophic level

what can we view a natural environment as?

we can view a natural environment (e.g. a forest, coral reef, desert, etc.) as a system that absorbs, transforms, and stores energy. in this view, physical, chemical and biological structures and processes are inseparable. when we view an environment this way we view it as an ecosystem. careful: unlike nutrients and water, energy does NOT cycle through an ecosystem! in other words, energy flows through an ecosystem and exits as it is lost through the process of cellular function. energy does not get cycled in the soil and then pulled back into plants.