Chapter 2

Living and Non-Living Things Interact in Ecosystems

2.1 Types of Interactions inEcosystems

Symbiosis

PSymbiosis is the relationship between two differentspecies in an ecosystem. Sometimes thisrelationship is good while other times it’s not.

Types of Interactions in EcosystemsSymbiosis

PThere are THREE types of symbiosis.

P1. Parasitism is a type of symbiosis where onespecies gets a benefit while the other species isharmed in some way. In extreme cases the host maydie.

PThe parasite obtains its food from the other organismwhich is called the host.

PParasites can be external or internal

Scabies mite

Examples of Parasites

Tomato Hornworm covered in Braconid Wasp pupae

Human Tapeworm

Fungal parasite onMaple tree Cordyseps Fungus

on Carpenter Ant

Raflesia parasitzes a grape plant

Types of Interactions in EcosystemsSymbiosis

P 2. Mutualism is a type of symbiosiswhere both species in the relationshipget a benefit.

P Termites cannot digest wood, so a typeof single-celled organism that can digestwood lives in their digestive system. The termites are providing the micro-organism with a place to live and a foodsource and in turn, the micro-organismbreaks down the wood into simplesugars that the termite can use for a foodsource.

Examples of Mutualism

Bees get nectar, flowers get pollinated Crocodile and Egyptian Plover

Lichens - mutualism between fungus & algae

Ants and aphids

Types of Interactions in EcosystemsCommensalism

P3. Commensalism is when there is a relationshipbetween two organisms where only one of themgains a benefit. The other does not get any benefit,but it is not harmed either.

Clown fish and sea anemone Woodpecker living in a tree Barnacles on a whale

P. 37 # 1-3

Types of Interactions in EcosystemsFood and Populations

PThe relationship between predator and prey is alsosymbiotic.

PThe predator keeps the prey animal populationunder control by hunting it.

P If the population of the prey animal goes down, itbecomes harder for the predator to get food. As aresult, the population of the predator goes downtoo.

P In this way, there is always a balance in theecosystem.

Checking Concepts

P. 39 #1-7

2.2 Roles of Organisms inEcosystems

PAll living things must have a food source.

PWe can classify organisms based on what they eat.

P1. Herbivores are organisms that consume onlyplant material.

P2. Carnivores are organisms that eat only otheranimals.

P3. Omnivores are organisms that eat both plant andanimals.

2.2 Roles of Organisms inEcosystems

PWe can also classify organisms onhow they get food - 4 ways....

P1. Organisms that must consumeother organisms, whether they areanimals or plants are calledconsumers.

P2. Organisms that can produce theirown food, such as green plants, arecalled producers.

Roles of Organisms in Ecosystems

P3. Organisms that feed off dead organisms or thewaste of other organisms are called scavengers.

Roles of Organisms in Ecosystems

P4. Organisms that break down dead organisms orthe waste of organisms into their basic chemicalparts are called decomposers.

Decomposers in our Food

PThere are two basic ways to prevent decomposers,such as mold and bacteria, from growing on ourfood.< 1. Keep them off the food in the first place, by making

sure our hands are clean before handling food, usingclean utensils to prepare food and by keeping food wellcovered and sealed.

< 2. Slow down or prevent the growth of decomposers byusing methods like refrigeration, canning, vacuumpacking, freezing, freeze-drying or radiation.

Decomposers in our Food

P Drying removes moisture which all organisms require tosurvive.

Freezing removes warmth thus slowing or stoppingreproduction

P Radiation kills bacteria.

P Canning and vacuum packing removes air. Withoutoxygen most organisms cannot survive.

P Salting food prevented growth of bacteria ex salt cod orpickling food in brine

P Pickling food prevents harmful bacteria from growing,since bacteria have a hard time surviving in vinegar.

Decomposers in our Food

P Sometimes the growth of these decomposers are helpful to us

P For example, we use a friendly form of bacteria to produceyogourt and sour cream. This type of bacteria will not makeus sick, in fact, it helps keep us healthy by preventingharmful bacteria from growing in our intestines.

P There is a type of yeast (a form of fungus), that will turnsugars into alcohol and produce carbon dioxide bubbles. Weuse this yeast to make bread, cheese, beer and wine.

P The main reason for using yeast in making bread is to get thedough to rise so that when baked it is light and fluffy. Theyeast does this with the carbon dioxide bubbles. The alcoholproduced is evaporated when baked.

2.3 Food Chains, Food Webs & Energy Transfer

Food Chains

PGreen plants and algae require energy from the sunto make food.

PThe plants and algae use some of this energy fortheir own life processes. When a herbivore eatsthem, some of the trapped energy is passed on to theanimal.

PA carnivore eats the herbivore and some of theenergy the herbivore consumed is passed on to thecarnivore.

Food Chains, Food Webs & Energy Transfer

Food Chains

PThe transfer of energy from organism to organism isreferred to as a Food Chain.

The arrowsshow theflow ofenergy!

As you goup the foodchain, theamount ofenergypassed onisdecreased!

Roles of Organisms in Food Chains

PEach type of organism has a role in the food chain.

PEvery food chain must have a producer at thebottom.

PProducers trap the energy from sunlight through aprocess called photosynthesis. It is this energy thatis passed up the food chain.

PThe next level of a food chain are organisms calledherbivores. They eat plants only and are calledprimary consumers because they are the first in theline of consumers in any food chain.

Roles of Organisms in Food Chains

PThe next level of consumers are those that eat otherconsumers. We often call them carnivores, but in afood chain they are called secondary consumers.

PFood chains usually have up to four links, but itcan’t be too much longer since energy begins to runout as the food chain gets longer.

As you go up theenergy pyramid,there is less andless energytransferred.

To get the sameamount of energy,the organism hasto eat more.

PrimaryConsumer

SecondaryConsumer

Roles of Organisms in Food ChainsFood Webs

PEvery organism is a member of a food chain. However, it is rare that an organism is a member ofonly one.

P In fact, most organisms are members of several foodchains. When several food chains cross over oneanother in the same ecosystem like this we call it afood web.

POf course, the last stage of any food web are thedecomposers. Anything that dies in the food webwill be broken down by decomposers.

Food Web

Energy Transfer in Food Chains

P When an organism eats, it is consuming food for energy. Most of this energy is being used for life processes suchas respiration, growth and movement.

P Another large portion of the energy is passed out of theanimal in the form of waste products such as gases, solidwaste or urine.

P Only about 10% of all the energy that an organismconsumes is actually stored in the animals living tissues.

P That means the second organism that eats this firstorganism is only getting about 10% of all the energy thatit consumed.

Energy Pyramid

2.4 Cycles of Matter in Ecosystems

Nutrients

PFood provides more than just energy to organisms.

PNutrients such as carbon and nitrogen are alsocontained in food.

PNutrients are used for growth and repair of theorganisms body.

PProducers get their nutrients from the soil, water andair.

PConsumers get their nutrients from the foods that theyeat.

Cycles of Matter in Ecosystems

Nutrients

PThere is only a limited supply of nutrients on theplanet. Therefore, nutrients must be used over andover again.

PWhen the nutrients are in the soil, air or water they areabiotic but when these nutrients are used in thegrowth and repair of an organism they are biotic.

PThe process that moves nutrients from organisms tothe soil and from soil to organisms is called thenutrient cycle. (See P. 61)

Nutrient Cycle

Cycles of Matter in EcosystemsSteps in the Nutrient Cycle

P 1) Plants absorb nutrients from the soil, water or air.

P 2) Primary consumers eat plants and Secondary consumerseat other animals. In both cases, nutrients are passed tothem.

P 3) The consumers release some of these nutrients bybreathing out or excreting waste products (urine or feces).

P 4) The rest of the nutrients are held in their body structureuntil they die.

P 5) Decomposers take the dead organisms apart and place thenutrients back into the environment to be used again byplants.