Ecology

Ecology

Definitions
1. Abiotic: Non living components
2. Biotic: Living components
3. Heterotroph : gains energy by consuming other organisms
4. Ecology: the study of interactions between organisms and their environment
5. Population: all organisms of 1 species that reside in the same space
6. Habitat: where an organism lives
7. Community: a space where many different species reside at the same time. They interact together
8. Autotroph: An organism that can manufacture its own energy from inorganic substances or light
9. Niche: The role of an organism within an ecosystem including where it lives, what it eats and its effect on the ecosystem
10. Biome: A category within the biosphere containing all the plants and animals in a region
Trophic levels: a level in a food chain defined by the method of obtaining food
1. 1. PRODUCERS: the plants and photosynthetic organisms 2. PRIMARY CONSUMERS: Herbivores 3. SECONDARY CONSUMERS: Carnivores 4. DECOMPOSERS: feeds on waste materials or dead organisms
2. As you go up the food chain, less energy is available. However, it is more energy efficient for people to consume carnivores because humans can’t fully digest all of a plant due to the cellulose
3. At higher tropic levels, there are fewer individuals because: - More needs to be consumed to meet their energy demands - More completion
4. Pyramid of Numbers: The area of the bars are proportional to the number of organisms at each stage
5. Pyramid of biomass: To obtain this data, organisms are all collected and burnt so that all the water has evaporated and only the tissue mass remains.. The area of the bar is proportional to the dry mass of all the organisms at that tropic level
6. Pyramid of energy: To obstain this data, all organisms are burnt in a calorimeter and the heat energy omitted from this is measured
7. Energy Content in a trophic level: Number of organisms × dry mean mass of 1 organism × energy content of 1g of dry mass
Productivity: the rate which energy passes through each trophic level (kilojoules of energy per m2/year)
1. Primary Productivity (mj/m2/year): the amount of energy fixed by photosynthesis
  1. Less than 1% if sunlight energy is reaching the earth is used for photosynthesis. Some light absorbed will also be lost as respiratory heat
  2. The rest are reflected by the earth’s surface, used to heat the atmosphere, evaporate water. Also different wavelengths of light may not be captured by chlorophyll
  3. Gross Primary Productivity: the rate at which plants convert light energy into chemical energy.
  4. The energy is lost between converting light energy into chemical energy and so less energy is left for primary consumers. The remaining energy is called Net Primary Productivity (kg/ha/year). This tells us how much energy is available to heterotrophs.
2. Secondary Productivity
  1. Primary consumers don’t always use up 100% of the plants biomass because: some plants don’t die, consumers are unable to consume the whole plant and most of the energy that is absorbed is used to keep the organism alive rather than to aid its growth
3. How to increase productivity
  1. Primary Productivity
    1. Planted earlier to provide a longer growing season when there’s more sunlight
    2. Grow in light banks
    3. Irrigating crops
    4. GM crops that are drought resistant/ mores responsive to fertiliser/ pest- resistant
    5. Grow in greenhouse to generate heat
    6. Crop rotation to increase the amount of nutrients available in the soil
    7. Plant lots of nitrogen fixing crops around the crops to replenish the nitrate levels
    8. Use pesticides to remove pests and increase the yield
    9. Herbicides to kill weeds and reduce competition
    10. Fungicides: Fungi can cause fungal rot, damage to xylem/ phloem tubes
  2. Secondary Productivity
    1. Harvesting animals just before adulthood when the young animal is using most of its energy in growth
    2. Steroids (no longer used in the UK)
    3. Selective breeding
    4. Animals treated with antibiotics so that less energy is used to treat infections
    5. Reduce the animals movements as much as possible
    6. Maintain the optimal temperature for them
Succession: is the directional change in a community of organisms over time
1. Sere: distinct stages with the non- living environment becoming less hostile
2. Pioneering Species: starts succession and can begin on many different substrates.
3. 1. Algae and lichens are the first to live on the bare rock: this is the pioneering community. These plants are resistant against salty water, unstable sand and strong winds
4. 2. The algae erodes through the rock and when it dies, the rot produces soil for larger plants to grow.
5. 3. The wind blows the sand and a sand dune is created. The roots of any vegetation here hold the sand together to stabilise it. For example, marram grass helps make the area more stable by catching and trapping sand.
6. 4. The increased stability helps other plants grow and allows nutrients to be accumulated
7. 5. Moss and ferns develop and when they die, even larger plants succeed them. These are called: Climax Community.
8. 6. Other plants such as nitrogen fixing bacteria grow and this helps increase the concentration of nitrates in soil
Diversity
1. Key Words
  1. Reliable: if the study were repeated, would it produce very similar results
  2. Representative: gives a good overall picture of the variables you are measuring
  3. Unbiased: no human influences on the results
2. Types of sampling
  1. Random Sampling: a random coordinate generator is used
  2. Stratified Sampling: used when there’s multiple areas with contrasting conditions
  3. Systematic Sampling: when samples are taken over a transect
    1. Line transects (observing what species is found at 1 point touching the tape)
    2. Belt transects (the quadrat is placed at certain points along the tape)
  4. Methods
    1. Density: counting the number of individuals
    2. Percentage cover: estimate what proportion of your quadrat is covered by your species
    3. Biomass: collect, dry and weigh all the living matters of your chosen organism from within your quadrat
    4. Relative Abundance: choose a category to describe the abundance: (Abundant, common, frequent, occasional, rare)
    5. Percentage frequency: using a quadrat or point (does the organism touch the corner of each box. Each touch equates to 1%)
    6. Calculations
      1. Species Abundance: the number of individuals in each species
      2. Species Richness: the number of different species
      3. Species Diversity: takes both abundance and richness into account
        Simpson’s Diversity Index
3. Population Size
  1. K- strategist and R- Strategist
    1. K-Strategist: species whose population is determined by the carrying capacity. The population tends to have a low reproductive rate and have slow growth. Tend to be large
      1. The limiting factor exerts a bigger effect on the population as the population is very close to the carrying capacity
    2. R-strategist (the “boom and bust” pattern): the population size increases so rapidly that it exceeds the carrying capacity of the habitat before limiting factors start to have an effect. Tend to be small
      1. Once the carrying capacity has been exceeded, there’s no longer enough resources ot support all the individuals and this leads to the DEATH PHASE.
  2. Growth Curve
    1. Carrying capacity: is the maximum population size that can be maintained over a period of time in a particular habitat
    2. 1. Lag phase: there are only a few individuals in the population and they are still acclimatising. The rate of reproduction at this stage is low
    3. 2. Log phase: resources are plentiful and the conditions are advantageous. This means the rate of reproduction is fast and exceeds the mortality rate.
    4. 3. Stationary phase: the population size levels out at the carrying capacity of the habitat. The habitat cannot support a larger population. There might still be small fluctuations. The rate of reproduction and mortality are equal
  3. Predators and Prey
    1. 1. Large population of predators means more prey are eaten
    2. 2. The number of prey decrease= less food for predators
    3. 3. Fewer predators= the prey population can recover and increase
    4. 4. The prey population increases= more predators
    5. Cycle repeats
4. Competition happens when there’s a lack of resources available to support all of the individuals present
  1. Intraspecific competition: occurs between individuals of the same species
  2. Interspecific competition: occurs between individuals of different species
    1. More overlap between 2 species’ niches would result in more intense competition
    2. Competitive Exclusion Principle: if 2 species have the same niche, one would be outcompeted by the other and this would result in extinction
  3. Allelopathy: is a form of competition because it stops neighbouring organisms from using resources in the habitat
    1. An organism releases a chemical and this chemical inhibits growth, germination or nutrient uptake
    2. Black Walnut Trees: releases JUGLONE, which inhibits respiration in neighbouring plants. This gives young walnut trees better access to light
    3. Sorghum: releases sorgolene through its roots and prevents respiration in neighbouring plants.
Sustainable Growth
1. Small Scale Timber Production
  1. Coppicing: cutting a tree trunk close to the base to encourage new growth.
    1. 1. Cut the DECIDUOUS TREES (the ones that shed leaves)
    2. 2. Lots of new shoots grow from the cut surface.
    3. 3. The narrow branches can be used in fencing, firewood or furniture
    4. 4. The branches are cut and new shoots regrow
      1. This can sometimes be done as Rotational Coppicing which is when the woodland is divided into 2 and only 1 half is harvested to allow the other half to grow. This is more sustainable and encourages biodiversity. If the woods were left, it is hoped that it would return to normal
      2. Some trees are left to grow without being coppiced. They are called standards and provide larger pieces of timber
  2. Pollarding: This is similar to coppicing but the tree trunks are cut a little higher up to prevent deer and other wildlife from feeding off the emerging shoots.
2. Large Scale Timber production
  1. Clear felling: this destroys habitats on a large scale and involves cutting all the trees in an area
    1. This reduces soil mineral levels and makes it more susceptible to flooding, erosion
    2. The soil could also contaminate rivers
    3. Sometimes, the area is clear felled but then left to mature for 50-100 years before felling again to allow the biodiversity to increase
    4. Modern sustainability forestry encourages that: the trees which are harvested are then replaced by another tree. The woodland must also maintain its ecological function and the local people should benefit from the forest.
    5. Only the largest and most valuable trees are removed
3. Management
  1. Control pests/ pathogens/ poachers/ predators
  2. Only plants trees that will grow well in that environment
  3. Position trees/ animals with distance between them to reduce competition
  4. Raise carrying capacity
  5. Move organisms to other areas which they might be able to benefit more from
  6. Vaccinate animals
  7. Set up SSI, National Parks or ex situ zoos/ botanical gardens
4. Conservation: involves maintenance of biodiversity between species, genentic diversity within species, habitat and ecosystem
  1. Humans
    1. Over exploitation of wild population for food/ commerce
    2. Habitat disrupted or fragmented
    3. Species introduced to the ecosystem by humans may outcompete the native species
  2. Reasons for Conservation
    1. Food source: genetic diversity of wild stands could be used to breed for disease/ drought resistance or improved yield
    2. Medicinal drugs
    3. Biological control agents
    4. Pollinating crops
    5. Maintaining water quality
    6. Climate stability: global warming, preventing floods
    7. Ecotourism
Galapagos
1. Information
  1. 50% of vertebrate species and 25% of plant species are endangered
  2. Population has increased from 5000 residents and 4000 tourists to 28,000 residents and 100,000 tourists from 1980 to 2005
  3. Forests of Scalesia trees and shrubs have almost been completely eradicated in Santa Cruz and San Cristobal
2. Habitat Destruction: increased demand for resources
  1. Limit tourists
  2. Increase protected areas
  3. Encourage emigration and prevent further immigration
  4. Careful city planning to prevent habitats from being fragmented
3. Pollution: increased need for oil and increased production of waste
  1. NOTE: Oil spill in 2001 caused damage to marine and costal ecosystem
  2. Create no float zones or divert the ships
4. Overconsumption: mainly of giant tortoises, sea cucumbers, sharks fin, fur and whales
  1. No take zones/ restrictions on what can be hunted and when it can be hunted
5. Newly introduced species vs. endemic species
  1. Red Quinine Trees: is an invasive species on Santa Cruz. It outcometes the Cacaolillo Strub and the Scalesia trees. This has also caused the Galapagos Petrel to lose it's nesting site
  2. The goat eats everything and outcompetes the giant tortoise. This increases soil erosion
  3. Cats and dogs attack birds and nests. They would even prey upon land tortoises and marine iguanas.

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