Ecology Study of how organisms interact with each other and with their environment

Levels of Ecological Organization Populations –groups of individuals of the same species living together in one area Communities –populations of different species living together in one area Ecosystems –communities and the non-living parts of the environment with which they interact

Population Structure Key aspects: Population Size Population Density Population Dispersion

Population Size Affects populations ability to survive small populations - more likely to go extinct

Population Density Number of individuals per unit area low density can be problem too

Population Dispersion Spacing of individuals within the population Random, uniform or clumped

Clumped dispersion is when individuals aggregate in patches. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 52.2a

By contrast, uniform dispersion is when individuals are evenly spaced. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 52.2b

In random dispersion, the position of each individual is independent of the others. Overall, dispersion depends on resource distribution. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 52.2c

Survivorship Curves Graphical representation of the survivorship (opposite of mortality) at each age

Survivorship Curves Type I –increased risk of dying when old Type II –equal chance of dying at all ages Type III –increased chance of dying when young

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 025 Proportion Surviving Human (type I) Hydra (type II) Oyster (type III) Percent of Maximum Life Span 10075

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Age (months) Proportion Surviving Poa annua – most like Type II

Population Growth Biotic Potential –r –the rate a population would grow at with no limits –intrinsic rate of increase

Exponential Growth dN/dt = rN r = (b - d) + (i - e)

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Number of Generations (t) Population Size (N) = 1.0 N dN dt

Carrying Capacity populations eventually reach a limit to their growth K = number of individuals that the environment can support

Logistic Growth dN/dt = rN ((K - N)/ K) growth rate slows as the carry capacity is approached sigmoid growth curve (S-shaped) most populations remain constant in size

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Number of Generations (t) Population Size (N) = 1.0 N = 1.0 N Carrying capacity 1000 – N 1000 dN dt dN dt

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. N = K Below KAbove K Population Size (N) Population Growth Rate (dN/dt) 0 Negative Growth Rate Positive Growth Rate Carrying Capacity (K)

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display a.b Number of Cladocerans (per 200 mL) Number of Breeding Male Fur Seals (thousands) Time (years) Time (days) Logistic Growth

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display B.C B.C B.C B.C. Billions of People Significant advances in public health Industrial Revolution Bubonic plague “Black Death” Year

Limits to Population Growth Resource limitation- competition predation

Community Ecology Study interactions among populations Niche –total of all the ways an organism uses resources in its environment –food consumption, space utilization, temp range, etc... Habitat –physical location

Competition struggle between organisms to utilize the same resource when the resource is limited niches overlap and resources are limited

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. High tide Low tide C.stellatus fundamental and realized niches are identical when S.balanoides is removed. S.balanoides and C.stellatus competing Chthamalus realized niche Chthamalus fundamental niche Semibalanus realized niche Semibalanus fundamental niche J.H. Connell’s classical study of barnacles

Competition “fighting” = interference competition consuming shared resources = exploitative competition

Competition Interspecific competition –between individuals from different species Intraspecific competition –between individuals from same species

One Possible Result of Competition Competitive exclusion –no species can occupy the same niche indefinitely –one species will be outcompeted and be driven to extinction locally

Fig Gausse’s Experiments Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display a. Days Paramecium caudatum Paramecium aurelia Paramecium bursaria Population Density (measured by volume)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Days Paramecium caudatum Paramecium aurelia Paramecium bursaria Population Density (measured by volume) b. Competitive Exclusion

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. c Days Paramecium caudatum Paramecium aurelia Paramecium bursaria Population Density (measured by volume) Coexistence…Resource Partitioning

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display a. c Days Paramecium caudatum Paramecium aurelia Paramecium bursaria Population Density (measured by volume) Population Density (measured by volume) Population Density (measured by volume) b

Other Results of Competition Niche overlap can lead to... –Resource partitioning –character displacement

–Resource partitioning is the differentiation of niches that enables two similar species to coexist in a community. Fig Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Character displacement is the tendency for characteristics to be more divergent in sympatric populations of two species than in allopatric populations of the same two species. –Hereditary changes evolve that bring about resource partitioning. Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Predation Predator uses prey for food prey evolves defenses, predator evolves adaptations to overcome…arms race

Predation Plant defenses against herbivores: morphological - thorns, spines, plant hairs chemicals - secondary compounds

Animal defenses against predators: Behavioral defenses include fleeing, hiding, self-defense, noises, and mobbing. Predation

Camouflage includes cryptic coloration, Leaf mimic katydid from the Ecuadorian Amazon

Deceptive Markings: eyespots dyoftheflowers/ /

Mechanical defenses include spines & shells. african-safari-pictures.com

Chemical defenses include odors and toxins – may get them from the plants they eat (ex: monarch butterfly & milkweed) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Aposematic coloration is indicated by warning colors, and is sometimes associated with other defenses (toxins). Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Mimicry is when organisms resemble other species. –Batesian mimicry is where a harmless species mimics a harmful one. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Müllerian mimicry is where two or more unpalatable species resemble each other. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 53.8

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Heliconius melpomene Papilio glaucusBattus philenor a. Batesian mimicry: Pipevine swallowtail butterfly (Battus philenor) is poisonous; Tiger swallowtail (Papilio glaucus) is a palatable mimic. Heliconius erato Heliconius cydnoHeliconius sapho b. Müllerian mimicry: Two pairs of mimics; all are distasteful.

Predation Can promote species diversity predator eats superior competitor

Keystone species exert an important regulating effect on other species in a community. Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

If they are removed, community structure is greatly affected. Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Coevolution & interspecific interactions –Coevolution refers to reciprocal evolutionary adaptations of two interacting species. When one species evolves, it exerts selective pressure on the other to evolve to continue the interaction. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

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