We share the earth with all of the other creatures; removing any organism from an environment can have many diverse consequences - not always

Transcription

1 Ecology

2 We share the earth with all of the other creatures; removing any organism from an environment can have many diverse consequences - not always predictable ones. Ecology is the study of the interactions of organisms with the living and nonliving parts of their environment. An interacting group of organisms and their environment constitute an ecosystem.

3 Habitat - place where a particular population of organisms live. Community - all the populations (of different species living together in the same habitat. Species diversity - the number of species living within an ecosystem. Ecosystems are made up of representatives of at least 5 of the 6 kingdoms. For example - there may be up to 100 species of trees living in just 1 hectare (2.5 acres) of a tropical rain forest.

4 No ecosystems are completely isolated although the physical boundaries are not always obvious. Natural changes in the physical environment of an ecosystem happen all the time. Ex. volcanic eruption forms a new island - sets off a process of colonization and ecosystem development.

5 How Organisms Interact in Communities

6 Interactions

7 Mutualism: Both Species Benefit Facultative: Helpful to both species Rhinos and oxpeckers Trees and fungi Ants and Acacia Pollination

8 Commensalism One member is helped, the other neither benefits or is harmed Epiphytes and forest trees Clown Fish and Anemone

9 Parasitism + and - relationship parasite benefits, host loses parasite usually smaller than host

10 Nematodes

11 What is Predation? Predation - one organism feeds upon the other How would coevolution of predator-prey prey happen? predator benefits from relationship prey is always harmed they evolve ways to protect themselves in response predator evolves way to counteract defenses of prey and so on

12 Predator Strategies Structural advantages Natural Weapons - Fangs, claws Flexible bodies Larger Size

13 Predator Strategies Ambush- Stalk a victim Venom Gape & Suck (fish) Keen eyesight

14 Predator Strategies SPEED & CUNNING More intelligent than prey Run faster than prey Hunt in packs

15 Prey Strategies Defense Techniques Inflate Flee Fight Back Stab Poison

16 Prey Strategies Structural advantages Hard Body Coverings Thorns or Spines Break away body parts Natural Weapons

17 Prey Strategies Chemical Warfare Blinding ink Poison Offensive Smells and Tastes

18 Prey Strategies Camouflage Cryptic (camouflage) coloration Aposematic (warning) coloration

19 Mimicry Mostly a prey technique Optical and sonic illusions LOOKS like a predator: School of fish; false eyes; frilled neck and inflation

20 Mimicry Batesian Mullerian

21 Plant-herbivore interactions How do plants defend themselves from herbivores? obvious ways - thorns, spines, etc. most contain defensive secondary compounds ex. include poison ivy and oak - produce a gummy oil mustard family - produce oils toxic to most insects for each group of plants there is usually a type of herbivore that can feed upon - often as their exclusive diet cabbage worms feed on mustard plants.

22 Competition When two species use the same resources, they are said to compete and their interaction = competition. ex. lions and hyenas compete for food in Africa Competition does not necessarily involve contact; interaction may be only by means of effects on the resources. No two organisms can occupy the same niche at the same time

23 Principle of Competitive Exclusion If two species try to occupy the same niche at the same time, one species will out- compete the other Example: Paramecium aurelia and Paramecium caudatum compete for the same resources. When introduced to a petri dish separately,, each grows well If grown together - P. aurelia will win (more resistant to bacterial waste products)

24 Competition evidence Resource partitioning~ sympatric species consume slightly different foods or use other resources in slightly different ways Character displacement~ ~ sympatric species tend to diverge in those characteristics that overlap Ex: Anolis lizard sp. perching sites in the Dominican Republic Ex: Darwin s finch beak size on the Galapagos Islands

25 The Niche Ecological niche: the sum total of an organism s use of biotic and abiotic resources in its environment; its ecological role Fundamental: the set of resources a population is theoretically capable of using under ideal conditions Realized: the resources a population actually uses Thus, 2 species cannot coexist in a community if their niches are identical Ex: Barnacle sp. on the coast of Scotland

26 Relationships Trophic structure / levels~ feeding relationships in an ecosystem Primary producers~ ~ the trophic level that supports all others; autotrophs Primary consumers~ herbivores Secondary and tertiary consumers~ ~ carnivores Detrivores/detritus~ ~ special consumers that derive nutrition from non-living organic matter Food chain~ ~ trophic level food pathway

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28 Relationships The path of energy through trophic levels of an ecosystem is called a food chain.. Food chains interconnect to form food webs. Energy is lost as heat at any energy transfer in a food web - generally not useful energy for biological systems. From a biological point of view, amount of energy decreases as energy passes through an ecosystem.

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30 Energy Flow Ecological efficiency: % of E transferred from one trophic level to the next (5-20% - rule of 10%) Pyramid of productivity: multiplicative loss of energy in trophic levels Biomass pyramid: trophic representation of biomass in ecosystems Pyramid of numbers: trophic representation of the number of organisms in an ecosystem

31 There is limit to the number of trophic levels in an ecosystem - maximum 3 or 4 because of this energy loss - a consequence of the 2nd law of thermodynamics. For example it takes a large population of zebras and wildebeests to support a small population of lions (1000 to 1!!!) Humans eat steak and hamburger at a great cost in energy. Cattle Ranching vs Agriculture Third World

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