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Option G.1: Community Ecology

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Option G.1: Community Ecology. Page 418. Vocab Recap. Community is a group of interacting populations living together and interacting with each other in an area Distribution of organisms in communities is affected by abiotic and biotic features .

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Presentation Transcript
vocab recap
Vocab Recap
  • Community is a group of interacting populations living together and interacting with each other in an area
  • Distribution of organisms in communities is affected by abiotic and biotic features
factors affecting distribution of plant species
Factors affecting distribution of plant species
  • Temperatureand water
  • Light
  • Soil pH
  • Salinity
  • Mineral nutrients
  • Turn and talk
    • Turn to your neighbor and discuss how theses factors affect plant distribution
    • Are these factors abiotic or biotic?
factors affecting distribution of animal species
Factors affecting distribution of animal species
  • Temperature
  • Water
  • Breeding sites
  • Food supply
  • Territory
  • Turn and talk
    • Turn to your neighbor and discuss how theses factors affect animal distribution
    • Which of these factors are biotic and which are abiotic?
random sampling
Random Sampling
  • Suppose you wanted to determine the size of a population
  • You could count every organism, but that would be very time consuming
  • Ecologists use a sampling method
  • They take a random sample and use it to estimate the total number of organisms
  • Samples must come from all around the habitat
    • Why?
  • In a truly random sample, each organism has an equal chance of being selected for the count
quadrat method
Quadrat Method
  • A quadrat is a square of a certain size
  • Organisms within the quadrat are counted
  • These counts are used to determine the population size
  • How to solve:
    • Calculate the average number of organisms in your sample quadrats
    • Multiply the average by the total number of quadrats
  • A scientist wants to determine how many beech trees and maple trees are growing on a dune. The scientists measures the area and divides it into 20 quadrats. Using a random sample table, five sample squares are selected and trees counted. The table on the next slide shows the data.
example continued
Example – continued
  • How many beech trees are there on the dune? How many maple trees?
example continued1
Example – continued
  • Take the average
    • Beech: 5.2
    • Maple: 8.4
  • Multiply the average by the total number of quadrats
    • Beech: 5.2 x 20 = 104
    • Maple: 8.4 x 20 = 168
  • Commonly used for studying how the distribution of plants in an ecosystem is affected by abiotic factors
  • Ecologists still draw quadrats and count the number of plant species of interest
  • They also measure the abiotic feature (e.g. temperature, pH, light …)
the niche concept
The niche concept
  • Every organism in an ecosystem has a particular role in that ecosystem
    • That’s the organism’s niche
    • Concept includes where the organism lives (spatial habitat), what and how it eats (feeding activities) and its interactions with other species
    • What’s your niche?
spatial habitat
Spatial habitat
  • Unique space in the ecosystem
  • Area inhabited by any particular organism
  • The ecosystem is changed by the presence of the organism
  • Habitat loss is the greatest threat to biodiversity on our planet
    • What’s causing this?
feeding activities
Feeding activities
  • Affect the ecosystem by keeping other populations in check
  • For example, green frogs eat aquatic larvae of mosquitoes, dragonflies, and black flies
    • Green frogs keep these insect populations in check
interactions with other species
Interactions with other species
  • Competition
    • When two species rely on the same limited resource
    • One species will be better adapted than the other
  • Herbivory
    • A herbivore is a primary consumer (plant eater) feeding on a producer (plant)
    • The growth of the producer is critical to the well-being of the primary consumer
    • This is an interaction between plants and animals
interactions with other species1
Interactions with other species
  • Predation
    • A predator is a consumer (animal) eating another consumer (animal)
    • One consumer is the predator and the other is the prey
    • The number of prey affects the number of predators and vice versa
interactions with other species2
Interactions with other species
  • Parasitism
    • A parasite is an organism which lives on or in a host and depends on the host for food
    • The host is harmed by the parasite
    • Ex: plasmodium is a parasite that causes malaria in humans (reproduces in the liver and RBC); part of its life cycle take place in mosquitoes – mosquitoes are the vector
interactions with other species3
Interactions with other species
  • Mutualism
    • Two organisms living together where both organisms benefit from the relationship
    • Ex: clown fish and sea anemones
      • Clown fish are brightly colored and live within the area of the tentacles of the poisonous sea anemone
      • Clown fish are covered with mucus, which protects them
      • Clown fish lure other fish; sea anemone eats the fish and the clown fish eat the remains
competitive exclusion
Competitive Exclusion
  • No two species in a community can occupy the same niche
  • 1934; Russian ecologist G.F. Gause
    • Experiment with two different species of paramecium (P. aurelia and P. caudatum)
    • When each species was grown in a separate culture they did equally well
    • When the two were cultured together, with a constant food supply, P. caudatum died out and P. aurelia survived
  • When two species have a similar need for the same resources, one will be excluded
fundamental niche vs realized niche
Fundamental niche vs. realized niche
  • Fundamental niche
    • Potential mode of existence, given the adaptations of the species
      • No competition from other species
  • Realized niche
    • Actual mode of existence, which results from its adaptations and competition with other species
  • Total mass of organic matter
    • Organic matter = carbon compounds (carbs, lipids, proteins)
  • Since matter also includes water, which is not organic, it has to be dried
  • Biomass is measured as dry mass or organic matter of living organisms
  • Units = grams per meter squared per year
    • g m-2 yr-1
measuring biomass at each trophic level
Measuring biomass at each trophic level
  • How difficult is this?
  • There are tables and charts available which tell you the biomass of animal according to its size or weight
    • Ex: trap a raccoon, weigh it, then find its biomass in a table (raccoon should be returned to ecosystem)
  • There are tables for plant species, but it’s not easy to determine the weight of a tall tree
    • What to do?
measuring biomass cont
Measuring biomass – cont.
  • Measure the total area of the ecosystem
  • Divide the ecosystem into small areas & choose one plot to sample
  • Measure the size of each plant species (height and diameter)
  • Cut down all trees and vegetation
  • Dry them out
  • Mathematical model to show relationship between weight and height of each plant and its biomass
  • Sample other plots by measuring height and diameter (cutting down is not necessary)
measuring biomass cont1
Measuring biomass – cont.
  • If you are measuring the biomass of the ecosystem, then you would add in the animal species
  • Process is repeated seasonally or yearly to study changes in biomass over time
issues turn and talk
Issues – Turn and Talk
  • After measuring or counting organisms, we may fail to return them to the same ecosystem. Is there a moral principle involved here?
  • In order to measure biomass, destructive techniques are used – trees are cut down and plants are destroyed. Is this unethical?
  • Could the destructive sampling techniques described be explained as “moral relativism”?
  • List three factors that affect the distribution of animal species.
  • Explain the competitive exclusion principle.
  • Describe one technique that ecologists use to estimate accurately the size of a population of animals, including any calculations that need to be done.