Biology - An Illustrated Guide to Science (794127), страница 34
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Instead,this runoff empties into lakes, rivers,and streams and is carried back to theoceans, where the cycle begins again.● Some precipitation evaporates directlyback into the atmosphere.●76© Diagram Visual Information Ltd.Living cycle●This is globally insignificant but can belocally important.
Trees and vegetationgive out water by transpiration. Thisaffects the areas adjacent to thevegetation, creating pockets ofhumidity that affect the growth of arange of organisms. Animals haveminimal effect on the water cycle.3451234EvaporationWater in cloudsRain and snowWater drains into river and soil567Water taken up by plants and animalsWater loss by transpirationWater loss by respiration1195Energy flowECOLOGYKey wordsEnergy transfer and losscarnivorefecesherbivorephotosynthesisorganic matterenergy lost from the living system as heatsunlightenergyenergy flowing through the living systemIncomingAll energy in living systems isultimately derived from sunlight.● Photosynthetic plants capture energyin sunlight and use it to make sugar.This sugar provides energy for allother processes in the organism andresults in the creation of organicmatter.●producerTransferAnimals cannot carry outphotosynthesis and so get their energyfrom the organic matter stored byplants.● Herbivores eat the plants directly.Carnivores eat herbivores or othercarnivores that will—ultimately in thisfood chain—have eaten herbivores.●Energy lossprimaryconsumerSome energy is lost during transferbetween organisms.
Roughly 25percent of the food input for ananimal is wasted as feces. Another 25percent is used to keep the animalalive, which leaves only about 50percent that contributes to theproduction of new organic material.● These losses are repeated at everytransfer. This explains why food chainscan only be about four links long—ifthey were any longer, too muchenergy would be lost in each transferto make the chain sustainable.● The energy is given out as heat and isradiated from Earth into space.●secondaryconsumertertiaryconsumer© Diagram Visual Information Ltd.sunlightenergycapturedby plants(producers)196Pyramid of biomassECOLOGYKey wordsBiomassphotosynthesistrophic levelThe mass of organisms (biomass) that canexist at any given stage in a food chain ismuch smaller than that in the precedingstage.● This can be shown as a pyramid ofbiomass, in which different levels of thepyramid represent the biomass insuccessive stages of the food chain.● The base of the pyramid is the biomass ofprimary producers, and the peak depictsthe biomass of the top consumer.●Energy inputAll energy in living systems isultimately derived from sunlight.● Energy absorbed by green plants inphotosynthesis is used to build newcells.
These cells increase the size ofthe plants. The mass of material iscalled the biomass, and it is thebiomass that provides the energyinput for the next trophic level.●The base represents the algae and thepeak is the amount of human biomasscontributed by fish (i.e., bass) harvestedand fed to humans.● In this case, 10,000 kg of algae arerequired to produce 1 kg of human biomass,a huge difference that reflects the largeenergy losses at each stage of the foodchain.●Trophic level 5human (1 kg)Trophic level 4Trophic levelsPhotosynthetic plants are calledTrophic level 1. The animals that eatthem exist at Trophic level 2, and soon.● The biomass of all organisms at eachtrophic level is significantly lower thanthe biomass of the organisms in thelevel below.
When plotted on a graph,this shows itself as a pyramid—a pyramid of biomass.●Trophic level 3bass (10 kg)Trophic level 2animal plankton (1,000 kg)Trophic level 1© Diagram Visual Information Ltd.minnows (100 kg)algae (10,000 kg)197Food webECOLOGYKey wordsTypical food webdecomposedconsumerdecomposerfood chainfood webproducerconsumed bymountain lionsnakePrimary consumersSecondary consumersFeeding relationships●The relationship between an animaland its prey can be shown with anarrow. The arrow always points to theconsumer.Food chainsowlStarting with a single plant, it ispossible to plot a chain ofrelationships showing an animal eatingthe plant, the producer, and then thesame animal, the primary consumer,being eaten by another animal, thesecondary consumer, and so on.● Food chains typically have about fouror five links.●deerFood websThe feeding relationships in an areaare typically much more complex thana simple food chain.● A food web shows the ways that thefood chains in an area interact.
Manyorganisms will exist in more than onechain.●micerabbitsDecomposersDecomposers are not usually shown infood webs, but all living organismseventually die and are broken down bydecomposer organisms.● Since all organisms in the web wouldbe connected to this decomposerlevel, it would make a very complexdiagram that would be difficult tointerpret. For this reason, these linksare often omitted from more complexfood webs.DecomposersProducerscropsgrass© Diagram Visual Information Ltd.●trees198KEY WORDSKey wordsauxin Hormones that regulate plant growth.axial skeleton The skull, spine, rib cage, and pelvis.axon A long extension from the body of a nerve cellabdomen (1) The area below the rib cage and above thebacteriophage A virus that attacks bacteria.bacterium A microscopic single-celled organism that haslegs.
(2) In arthropods, the hind region of the body.© Diagram Visual Information Ltd.absorption The taking of dissolved substances into cells.active process A process that requires an energy inputfrom the organism.active site The part of the enzyme to which thesubstrate binds. It is where catalysis occurs.active transport The use of energy to transportsubstances across cell membranes against aconcentration gradient.adenosine triphosphate (ATP) A chemical in cells thatproduces the energy that drives biological processes.ATP becomes adenosine diphosphate (ADP) when itreleases its energy.adrenaline A hormone the body releases in situations ofstress.aerobic respiration Respiration requiring oxygen.allele Variants of the same gene.alveolus The sac-like end of an airway in the lungs.amino acid An organic compound that forms the basicstructural unit of proteins and peptides.amnion The fluid-filled sac that encloses the embryo.anaphase The stage of mitosis or meiosis in which thechromatids move to opposite poles of the cell.anaphase II The second anaphase stage in meiosis.antagonistic pair A pair of muscles that pull in oppositedirections.anther In flowers, the part of the stamen that producespollen.antibody A chemical produced by B lymphocytes thatattacks invading microorganisms.anticodon Set of three tRNA nucleotides that binds withits complementary codon in an mRNA molecule.antigen A chemical found in cell membranes and cellwalls that triggers the production of antibodies.aorta The artery that carries high-pressure blood awayfrom the left ventricle of the heart.artery A blood vessel carrying blood away from theheart under high pressure.asexual reproduction Reproduction in which offspringarise from a single parent.
It does not involve the unionof gametes. The offspring are identical to the parent.assimilation The use of absorbed materials to producenew cells in an organism.association neuron A neuron in the brain or spinalcolumn that forms the connecting link between sensoryand motor neurons.ATP See adenosine triphosphateauditory ossicle A bone in the middle ear that transmitsacoustic vibrations from the eardrum to the inner ear.autonomic nervous system The collection of nervesthat regulate the unconscious or automatic processes inthe body.along which impulses are conducted away from the cell.no nucleus.basal metabolic rate The energy expended by the bodyat rest to maintain vital functions.bilateral symmetry The property of being symmetricalon a vertical plane.bile Secretions made in the liver from the breakdown ofred blood corpuscles.biome A major ecological region with characteristicclimate and organisms.bond The chemical connection between atoms in amolecule.Bowman’s capsule A cup-shaped structure in thekidney where blood is first filtered.bronchiole One of two tubes in the lungs connectingthe bronchi to the alveoli.buccal cavity The cavity at the anterior end of thealimentary canal.calcification The deposition calcium in cartilage.cambium A layer of actively dividing cells between thephloem and xylem in flowering plants.canine tooth A long, pointed tooth used to tear food.capillary The smallest blood vessel in the body.carbon cycle The cycling of carbon through the livingworld by photosynthesis and respiration.carnivore A flesh eating animal.carpel The female reproductive organ of floweringplants, consisting of the stigma, style, and ovary.cartilaginous joint A joint in which bones are attachedby cartilage, e.g., the joint between the two halves ofthe pelvis.
The joint allows only slight movement.cell The basic structural and functional unit of anorganism.cellulose A polysaccharide molecule used to strengthencell walls in plants.central nervous system The brain and spinal cord.centriole The organelle in animal cells that controls theformation of the spindle during mitosis.centromere The center of a chromosome, where thechromatids are attached. It has no genes.cerebellum A part of the brain at the back of the headthat coordinates voluntary movement and balance.cerebral hemisphere One of two parts of the brain atthe top of the skull.
The cerebral hemispheres are theseat of conscious thought and voluntary movements.cervix The entrance to the uterus.chiasma The point at which nonsister chromatids ofhomologous chromosomes cross-over each other.chlorophyll A green pigment found in most plants thatabsorbs light energy during photosynthesis.chloroplast In green plants, an organelle in whichphotosynthesis takes place.199chromatid One of the two chromosome strands thatbecome visible during cell division.
The strands arejoined at the centromere.chromosome A threadlike structure in cells thatcontains genetic material.chyme The partially digested contents of the stomachbefore it passes into the duodenum.cilium A tiny hair found on the surface of cells andsome microorganisms.cloaca An opening through which the intestinal, urinary,and reproductive tracts empty in birds, reptiles,amphibians, and many fish.clone A genetically identical organism.cochlea The organ in the inner ear that converts soundinto nerve impulses.codon The triplet of bases held on the DNA that codesfor a particular amino acid.coenzyme Chemicals that are required by enzymes tocomplete a reaction.collagen The structural protein in connective tissue.colonial polyp A coelenterate that is attached to asubstrate and lives in giant colonies.concentration gradient A difference in theconcentration of a substance from one area to another.condensation reaction A reaction that binds twochemicals together and releases water.consumer An organism that consumes organic matter.continental drift The movement of large plates of theEarth’s crust.continuous variation Variation that shows a completespectrum of values, e.g., height or weight.contractile vacuole An organelle in many single-celledorganisms that expands and contracts to expel waterfrom the cell.cotyledon The leaf-like part of the plant embryo that isthe food reservoir.crista A fold of membrane projecting into the matrix ofmitochondrion.cyst A reproductive structure often strengthened byexternal walls to survive periods in inhospitable ordangerous conditions.cytoplasm The material that maintains a cell’s shapeand consistency.
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