Reading Essentials for Biology Glencoe, страница 6

Ecologists study organisms both in the lab andwhere the organisms naturally live.2. What do ecologists study?________________________________________________10Chapter 2READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Sharing the WorldNameDateClassSection2.1Organisms and Their Environment, continuedThe BiosphereThe biosphere (BI uh sfihr) is the portion of Earth that supports living things. It includes the air, land, and water whereorganisms can be found.The biosphere supports a wide variety of organisms in a widerange of conditions. Climates, soils, plants, and animals can bevery different in different parts of the world.

All over the world,though, living things are affected by both the physical, nonlivingenvironment and by other living things.3. What is the biosphere?________________________________________________________________________Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.How is the environment organized?The nonliving parts of the environment are called abiotic(ay bi AH tihk) factors. Some examples are temperature, moisture, light, and soil.

Ecology includes the study of abiotic factorsbecause they are part of an organism’s life. To truly know aboutmoles, for example, ecologists must learn the type of soil molesdig their tunnels in. To get a complete picture of the lives of trout,it is important to know the type of river bottom where they laytheir eggs.Living things also are affected by biotic factors. Biotic(by AH tihk) factors are all the living organisms in an environment. Even goldfish in a bowl are affected by fishes, plants, orother organisms that share their bowl. All organisms dependon others directly or indirectly for food, shelter, reproduction,or protection.4. Name four examples ofabiotic factors.________________________________________________________________________________________________Levels of OrganizationEcologists study individual organisms.

They study relationshipsamong organisms of the same species and connections amongorganisms of different species. They also study the effects of abiotic factors on species that live together. To make it easier toexamine all of these biotic and abiotic interactions, ecologists haveorganized the living world into levels. The levels are the organismby itself, populations, communities, and ecosystems.READING ESSENTIALSChapter 211NameDateClassSection2.1Organisms and Their Environment, continuedorganismpopulationcommunityecosystemA population is a group oforganisms that belongs to thesame species.

Population membersbreed with each other and live inthe same area at the same time.How organisms in a populationshare the things that they need intheir environment is important. Itmay determine how far apart theorganisms live and how large thepopulation becomes. Members ofthe same population may competewith each other for food, water,mates, or other resources.Some species have adaptationsthat reduce competition within apopulation.

For instance, frogshave a life cycle in which theyoung tadpoles and adult frogslook very different and have different diets. Tadpoles eat algaeand frogs eat insects; therefore,they are not competing with eachother for food.How do communities interact?No species lives entirely alone. Every population shares itsenvironment with other populations. This creates what is called abiological community. A biological community is made up ofdifferent populations in a certain area at a certain time.In a biological community, changes in one population maycause changes in other populations.

For instance, if the number ofmouse-eating hawks in a community increases slightly, the numberof mice in that community will decrease slightly. Other changescan be more extreme. For example, one population may grow solarge that it threatens the food supply of another population.In a healthy forest community, there are many populations thatdepend on each other. These might include birds eating insects,squirrels eating nuts from trees, mushrooms growing from decaying leaves or bark, and raccoons fishing in a stream. While thesepopulations are connected to each other, they are all affected byabiotic factors.

These relationships between different populations12Chapter 2READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.What is a population?NameDateClassSection2.1Organisms and Their Environment, continuedand their surroundings create an ecosystem. An ecosystem ismade of all of the different populations in a biological communityand the community’s abiotic factors.There are two major kinds of ecosystems—terrestrial andaquatic. Terrestrial ecosystems are those located on land. Examplesinclude forests, fields, and a rotting log. Aquatic ecosystems arefound in both freshwater and salt water.

Freshwater ecosystemsinclude ponds, lakes, and streams. Oceans are a type of saltwater,or marine, ecosystem.5. What is an ecosystemmade of?________________________________________________________________________Organisms in EcosystemsDifferent types of organisms make their homes in differentplaces. Some species of birds live in only one type of forest.

Inthese areas, they find food, avoid enemies, and reproduce. Prairiedogs make their homes underground in grasslands. The placewhere an organism lives out its life is known as a habitat.6. What is a habitat?________________________________________________________________________Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.What place does a species have in its habitat?Though several species may share a habitat, the food, shelter,and other needed items in that habitat are often used in differentways by each species. For example, if you turn over a log, youmay find a community of millipedes, centipedes, insects, slugs,and earthworms. At first it might seem that the members of thiscommunity are competing for the same food because they all livein the same habitat, but each population feeds in different ways,on different things, and at different times.

Each species has itsown niche. A niche (neesh) is all strategies and adaptations aspecies uses in its environment. It is how the species meets itsspecific needs for food and shelter. It is how and where the speciessurvives and reproduces. A species’ niche includes all its interactions with the biotic and abiotic parts of its habitat.Two species cannot exist for long in the same community ifthey both have the same niche. There is too much competition.In the end, one species will gain control over the resources in thecommunity. The other species will either die out in that area,move somewhere else, or change in some way to fill another niche.READING ESSENTIALS7. Infer Which of the following does a polarbear use to survive inits habitat? (Circle yourchoice.)a.

burrowing instinct todig deep in the soilb. thick coat to protect itfrom the coldChapter 213NameDateClassSection2.1Organisms and Their Environment, continuedSymbiosisPeople once thought that animals in the same environmentfought each other for survival. In reality, most species survivebecause of the relationships they have with other species. A relationship in which there is a close and permanent associationbetween organisms of different species is called symbiosis(sihm bee OH sus).

Symbiosis means living together. Thereare three major kinds of symbiosis—mutualism, commensalism,and parasitism.________________________________________________________________________Commensalism Commensalism (kuh MEN suh lih zum) is arelationship in which only one species benefits and the otherspecies is not harmed or helped.

For example, mosses sometimesgrow on the branches of trees. This does not help or hurt thetrees, but the mosses get a good habitat.Parasitism Parasitism (PER uh suh tih zum) is a relationship inwhich a member of one species benefits at the expense of anotherspecies. For instance, when a tick lives on a dog, it is good for thetick but bad for the dog. The tick gets food and a home, but thedog could get sick. The tick is a parasite. A parasite is the organism that benefits from the relationship.

The dog is a host. Thehost is the organism that is harmed by the relationship.What relationship do predators and prey have?Another type of relationship is that between a predator and itsprey. Predators are organisms that seek out and eat other organisms. The organisms that are eaten are called prey. Predators arefound in all ecosystems. Some eat animals and plants. Some eatonly animals. Lions and birds that eat insects are predators.14Chapter 2READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.8.

What is the name of therelationship in whichboth species benefit?Mutualism Mutualism (MYEW chuh wuh lih zum) is a relationship between two species that live together in which bothspecies benefit. The relationship between ants and an acacia(uh KAY shuh) tree is a good example of mutualism.

The antsprotect the tree by attacking any animal that tries to feed on thetree. The tree provides nectar as a food for the ants. The tree alsoprovides a home for the ants. In an experiment, ecologists removedthe ants from some acacia trees. Results showed that the trees withants grew faster and lived longer than the trees with no ants.NameDateClassSection2.1Organisms and Their Environment, continued◗ After You ReadMini Glossaryabiotic (ay bi AH tihk) factors: nonliving partsof an organism’s environment; air currents,temperature, moisture, light, and soilare examplesbiological community: a community made up ofinteracting populations in a certain area ata certain timebiosphere (BI uh sfihr): portion of Earth that supports life; extends from high in the atmosphere to the bottom of the oceansbiotic (by AH tihk) factors: all the living organisms that inhabit an environmentcommensalism (kuh MEN suh lih zum): symbioticrelationship in which one species benefitsand the other species is neither harmednor benefitsCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.ecology: scientific study of interactions betweenorganisms and their environmentsecosystem: interactions among populations in acommunity and the community’s physicalsurroundings, or abiotic factorshabitat: place where an organism lives out its lifemutualism (MYEW chuh wuh lih zum): symbioticrelationship in which both species benefitniche (neesh): all strategies and adaptations aspecies uses in its environment; includes allbiotic and abiotic interactions as an organismmeets its needs for survival and reproductionparasitism (PER uh suh tih zum): symbiotic relationship in which one organism benefits atthe expense of anotherpopulation: group of organisms of the samespecies that interbreeds and lives in thesame place at the same timesymbiosis (sihm bee OH sus): permanent, closeassociation between two or more organismsof different species1.