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Chapter 53

BIOLOGY 1M03 Chapter 53: Chapter 53

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Ben Evans

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Chapter53CommunityEcology What is a Community • Is composed of all different interacting species living in a particular defined area • Different species live in close proximity  allow interactions Properties of Communities Species Richness • Number of different species in a community Ex. 24 species of trees on species Relative Abundance • Relative numbers (proportion) of individuals of each species in a community as a whole Ex. 30% conifers and 70% deciduous Diversity • Number and relative abundance of species in a biological community • Richness and relative abundance combined Ex. Of the 24 types of tree on campus, 30% are conifers and 70% are deciduous Two Explanations for Community Structure Individualistic Hypothesis: Gleason Focusses on single species • Community: o A chance (NOT STABLE, nor predictable) assemblage of species living in an area because they have similar abiotic requirements • Species: o Have independent distribution along environmental gradients with NO DISTINCT boundaries between communities Interactive Hypothesis: Clements • Community o A STABLE assemblage of closely linked species, having mandatory and predictable biotic interactions o Functions as an integrated unit • Species o Are clustered with DISCRETE BOUNDARIES between communities Rivet Model: P and A Ehrlich • most species in a community ARE closely associated with other species Redundancy Model: Gleason • most species in a community ARE NOT closely associated with other species Interspecific Interactions • Occur between populations of different species living together within a community and can be strong selection factors in evolution Symbiosis • an ecological relationship between two different species, whereby the host species and symbiont maintain close associations Commensalism (+/0) • Relatively rare on Earth • Symbiont benefits and host is unaffected Ex. Water buffalo with cattle egrets (bird) o Buffalo travel and step on grass, insects on grass fly into the air so don’t get stepped on o Cattel Egret are able to eat insects without affecting the buffalo o Cattle Egret: + Buffalo: 0 Mutualism (+/+) • Symbiont benefits and host benefits Ex. anacia tree and stinging ants o Acacia tree produces shelter for ants and nectaries(belting bodies) food o Acacia tree benefits from having the stinging ants on it because the ants sting animal that come to eat/stomp tree. Therefore, the tree is not eaten. o Ants bite away the plants that arch above it, allowing more photosynthesis Competition (-/-) • huge energetic costs to both so neither benefit Consumption (+/-) • predator benefits, prey doesn’t benefit Coevolution: involves a chande in one species that acts as a selective force st another species Counteradaptation: of the 2 species may affect selection of individuals of the 1 species THE INTERPLAY OF COEVOLUTION AND COUNTERADAPTATION BETWEEN THE PASSION FLOWER VINES (plassiflora) AND THE BUTTERFLIES (butterfly larvae- heliconius) • an arms race and counteradaptation between the plant and insects • not mutualistic PASSION FLOWER VINES (Passiflora) o produce toxic chemical to reduce herbivory tastes that bad (insect eats plants) BUTTERFLY LARVAE(Heliconius) o are able to tolerate the Passiflora chemicals, since they produce digestive enzymes, which break down the chemicals PASSION FLOWER VINES o produce nectaries that attract ants and wasps, which prey on Heliconiusbutterfly eggs and larvae o plant is counteradapting itself to make it work against the butterflies • Plant produces structures that look like insects eggs (nectaries) to try and deter the butterfly from putting the eggs there, because the butterfly doesn’t want its eggs to compete with others • if the butterfly lays eggs the eggs will eat the plant when they hatch • The nectaries attract wasps/bees which to eat the buteterfly eggs • GO OVER WITH SOMEONE TO GET PURPOSE OF WASPS Competition • Occurs when two or more species in a community rely on similar limiting resources Two Types of Competition: Interference • Involves actual fighting (direct physical contact) Ex. Deers fighting Exploitative • Involves consumption or use of resource • Still compete for resources but no direct contact Ex. Grocery shopping: brother eats before sister could get them or will eat leftovers • Niche overlap leads to competition exclusion • Competitive exclusion in two species of paramecium o In the overlap, there is a niche where they are competing for resources  not good o If overlapping niches, one will be competence and benefit/ die out o Or they will move apart to a new niche so they do not have competition o Cadautm will not succeed while Aurelia will survive (CEP) since it is a better competitor Competitive Exclusion Principle • In a stable environment, two species competing for the same limiting resource cannot coexist in the same community indefinitely • One will use resources more efficiently, thus reproducing more rapidly and eventually eliminates the other inferior competitor Types of Niches Ecological Niche • The sum total of an organism’s use of biotic and abiotic resources in its environment • Describes how an organism fits into an ecosystem Fundamental Niche • The resources a population is theoretically capable of using infer ideal circumstances • The combination of resources that the species uses in the absence of competitors • Where the organisms could potentially survive Realized Niche • The resources a population actually uses when competition occurs • Where organisms are actually positioned • Biological constraints restrict organisms to their realized niche o Ex. Competition, predation, resource limitation Experiment: Question: Why is the distribution of adult Cthamalus restricted to the upper intertidal zone? Hypothesis: adult Cthamalus are competitively excluded from the lower intertidal zone Null Hypothesis: Adult Cthamalus do not thrive in the physical conditions of the lower intertidal zone Prediction: Cthamalus will survive better in the absence of Semibalanus Prediction of Null Hypothesis: Cthamalus survival will be low and the same in presence or absence of Semibalanus Conclusion: Semibalanus is competitively excluding Cthamalus from the lower intertidal zone Fundamental niche: the combination of resources that the species uses in the absence of competitors Realized Niche: is that portion of the resources used when competition occurs Balanus is larger, more competitive, forcing Cthamalus to be higher. Balanus would die if not near water. Why is Resource Partitioning Important? • Allows similar species to co-exist in the same environment • Adaptation with increased frequency favoured by natural selection Ex. Warblers or Anolis Lizards (See diagrams) Predation • A predator eats prey • Animal- animal interactions or animal-plant interactions Parasitism • Predator lives in or on hosts, seldom involves death, parasite gets nourishment from the host Ex. A parasite that manipulates host behaviour o Can not live by itself o An infected ant’s butt turns red, and resembles berries that are eaten by birds o Ectoparasites: living on the surface of an organism  flees or tics o Endoparasites: live in the organism  worms in the gut of a dog Ex. Lungworm infection in Rocky Mount Big Horn Sheep o Resp. system can be infected and cause distress in sheep o Young/old are mostly effected o They have trouble breathing and throw up a lot of mucous on ground o Other sheep that are eating grass consume mucous and get parasite Parasitoidism • Insects/wasps lay their eggs on living host after hatching larvae will feed within host’s body and eventually causes its death Ex. Barcionid wasps lay eggs on hornworms 53.9 Constitutive defenses are always present (camouflage, schooling, weaponry) Characteristics Animal Predators • Acute senses, structures to catch/subdue/chew on prey, speed and agility, camouflage Plant defense against predators • Thorns, hooks, spines, chemicals, insect, hormones • Chemicals can confuse predators, with a death or mating pheromone to confuse insect • Help plant defend itself Ex. Pitcher plant o Has clear liquid inside so mice come and drink o The plant knocks them out with chemical and then break down the mouse biomass and consumes it o A carnivorous plant Types of Animals Defenses Utilized Against Predators: 1. Cryptic Colouration: camouflage • Makes prey difficult to see against its natural surrounding • Requires the animal to remain still to avoid detection • Only can see when moving around • Ex. Praying mantis o Can be diff colours to match the flower colour Ex. toad o Matches tree bark Ex. Tree hoppers o Similar to grass hoppers and look like a spikes on a bark of tree Ex. Stick bug (walking sticks) o Move very slowly on a branch to not be noticed Ex. While plumage of a bird during the winter season 2. Aposematic Colouration “Warning Colouration” • Bright colouration • A warning of effective mechanical or chemi
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