Leaving Certificate Agricultural Science

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Leaving Certificate Agricultural Science
Ecology
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Introduction

• Ecology is the study of how living things
  interact with each other and with their
  environment.
• The Biosphere is the part of the earths land,
  air and water where life can survive and grow.
• The biosphere has two main divisions, aquatic
  (water) and terrestrial (land) environments.

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Introduction - 2

• The aquatic also consists of marine and
  freshwater.
• The terrestrial is divided into biomes, which are
  determined by the dominant plants there E.g.
  Tropical rain forests, temperate deciduous
  forests, grasslands, tundra etc.
• The types of plant growing in a biome influences
  what other animals or plants live there and
  provide food and habitats (places to live).

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Ecosystems

• An ecosystem is a community of organisms
  interacting with each other and their
  environment.
• An ecosystem can be any size e.g. a rocky
  seashore, a tropical rainforest, a lake or even a
  garden pond or compost heap.
• An ecosystem is made up of living (biotic) and
  non-living (abiotic) parts.
• The abiotic part is called a habitat- a habitat
  is the type of place an organism normally lives.
• Different abiotic factors influence what species
  of plant or animal can live in a habitat.

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Ecosystems - 2

• Examples of abiotic factors include Temperature,
  water, light, humidity, currents, soil, pH, wave
  actions, topography etc.
• The biotic part is called a community, which is
  made up of a series of populations of animals and
  plants.
• A population is a group of individuals of the
  same species, each adapted to live in their
  particular habitat.
• Biotic Factors are also evident in an ecosystem,
  including what animals and plants live there,
  which may provide food, competition or threat of
  being eaten.

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Producers and Consumers

• Animals and plants are classified in ecology by
  how they feed.
• Producers are organisms that use light energy to
  make their own food from simple chemicals in
  their environment.
• Green plants are producers and are generally
  found at the bottom of the food chain.
• Consumers are organisms that do not make their
  own food but obtain their energy from the tissues
  of other organisms.

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Producers and Consumers - 2

• Consumers are classified further depending on the
  types of food they eat.
• Herbivores
• Carnivores
• Omnivores
• Decomposers
• Detritus feeders (Detritivores)
• Detritus is dead decaying organic matter.

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Food Chains and Food Webs

• A food chain is a straight-line sequence of what
  eats what in an ecosystem.
• A food web is a more accurate picture of what eat
  what, because most organism belong to more than
  one chain.

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Types of Food Web

• There are two main types of food web
• In a grazing food web, the energy flows from
  green plants to herbivores and then through a
  series of carnivores.
• In a detritus food web, the energy flows from
  green plants through detritus feeders and
  decomposers.
• Each food chain has a number of trophic levels.
• A trophic (feeding) level is a step on a food
  chain at which an organism obtains its food.

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Trophic Levels

• 1st Trophic Level producers (green plants)
  producing sugars and proteins through
  photosynthesis.
• 2nd Trophic Level primary consumers that feed
  directly on the producers.
• 3rd Trophic Level secondary consumers
  (carnivores that feed on primary consumers).
• 4th Trophic Level tertiary consumers
  (carnivores that feed on other carnivores.
• Decomposers and Omnivores (including humans) may
  appear at different trophic levels.

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Ecological Pyramids

• Food chains indicate what eats what, but doesnt
  indicate the numbers involved or how big they
  are.
• There are two types of ecological pyramids,
  pyramids of numbers and pyramids of biomass.
• Biomass is a term used to describe the mass of a
  population.
• A pyramid of numbers is a bar chart indicating
  the relative numbers of organisms in a food
  chain.
• A pyramid of biomass is a bar chart indicating
  the relative total mass of the population of a
  species in a food chain (detail to follow)

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Nutrient Recycling

• Elements are the raw materials of life.
• The most important elements are Carbon (C),
  Hydrogen (H), Oxygen (O), Nitrogen (N),
  Phosphorous (P) and Sulphur (S).
• 95 of our bodies are made up of these elements.
• Like energy, matter (elements) cannot be created
  or destroyed. This means that elements are
  recycled throughout an ecosystem.
• Decomposers and detritus feeders play a huge part
  in this recycling.

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Nutrient Recycling - 2

• There are three major cycles where elements are
  recycled. These are the water cycle (H and O),
  the Nitrogen cycle (N) and the Carbon cycle (C).
• A significant amount of stored carbon in fossil
  fuels is now being converted to CO2 or CO, which
  are greenhouse gases.
• The greenhouse effect is a natural phenomenon
  where the layers of gases in our atmosphere trap
  heat energy.

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Environmental Factors in Detail

• Abiotic factors are non-living parts of an
  ecosystem, which determine which animals or
  plants live there.
• Biotic factors are living parts of a community,
  the animals and plants that live there, and again
  they determine what organisms live in the
  ecosystem.
• Abiotic factors can be divided into CLIMATIC and
  EDAPHIC factors.

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Climatic Factors

• Climate refers to the average weather conditions
  in an ecosystem
• Features that affect climate include latitude,
  altitude, the sun and day / night
• These features interact to produce winds and
  currents, which influence the soils of the world.
  
• The soil conditions influence green plant
  (producers).
• Climatic factors include

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Climatic Factors 2

• Light
• Temperature
• Air (oxygen)
• Water (rain fall etc)
• Humidity
• Wind
• Topography (angle, aspect and altitude)

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Edaphic Factors

• Edaphic factors are related to soil texture, soil
  pH, soil nutrient availability, organic matter
  content and water content.
• The soil is the uppermost layer of the earth
  crust. It consists of rock, organic matter, air,
  water, minerals and living organisms.
• The soils functions are to
• Provide plants with anchorage.
• To supply water, nutrients and air to plants.
• To house millions of microorganisms.

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Edaphic Factors - 2

• The structure and fertility of soils depend on
  its composition and relative amounts of sand,
  silt and clay.
• Soil Fertility refers to the amount of nutrients
  available for good plant growth.
• The properties of soil are heavily influenced by
  climate and topography.
• Soil is formed by the breakdown of rock by either
  physical weathering (freeze thaw) or chemical
  weathering (acid rain).
• Soil particles (sand, silt and clay) are
  classified by their diameter.
• Clay lt 0.002mm
• Silt 0.002 to 0.06mm
• Sand 0.06 to 2.0mm

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Edaphic Factors - 3

• The relative amounts of sand, silt and clay
  affect a number of soil conditions
• Predominately sandy soils have good aeration and
  good drainage but therefore leach minerals.
• Clay soils have poor aeration, poor drainage but
  higher mineral content.
• The best soils are loams which contain similar
  amounts of sand and clay, therefore have good
  drainage, good aeration and do not leach minerals.

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Soil Components

• The main components of the soil that affect the
  ecosystems are
• Organic Matter Content
• Humus is decomposing organic matter.
• Humus improves soils aeration, drainage.
• Decomposers break down humas releasing minerals
  into the soil.
• Soil Water
• Water is absorbed by plant roots and used in
  photosynthesis.

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Soil Components - 2

• Soil Air
• Air, containing oxygen, is essential respiration.
• The amount of air is dependant on the amount of
  sand and clay in the soil.
• Soil pH and Nutrients
• Soil nutrients are made available by decomposing
  organic matter (or fertilisers).
• pH levels of soil affect the availability by
  these minerals.
• Irish soil pH values vary from 3.5 in peat bogs
  to 8.5 in brown earths of Wexford.

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Soil Components - 3

• Soil Organisms
• The varying organisms in soil affect a number of
  soil conditions.
• Decomposers make minerals available to the soil.
• Earthworms introduce air and minerals to the
  soil.
• Nitrifying Bacteria produce usable nitrates from
  N2

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Biotic Factors in and Ecosystem

• Biotic factors are the influences due to other
  organisms in an ecosystem.
• The main biotic factors are
• Competition
• Organisms compete for different resources in
  their ecosystem e.g. food, shelter.
• Competing organisms are said to have the same
  niche.
• A niche is the role of an organism in an
  ecosystem.

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Biotic Factors - 2

• Adaptations
• Adaptations are ways in which an organism is
  specialised, in its body structures or
  behaviours, to survive and reproduce in that
  habitat.
• There are many examples of plant and animal
  adaptations
• Cacti have no leaves but spines to prevent water
  loss.
• Seaweeds have a slimy layer to prevent water loss
  when not submerged in water.

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Biotic Factors - 3

• Plants
• Plants must compete for root space, light, water,
  nutrients, pollinators and seed dispersers.
• They adapt by changing life style or structures
  to survive.
• Animals
• Animals compete for food, water, shelter and
  mates.
• They must also avoid being eaten.
• They adapt by camouflage, changing behaviour,
  structures or life style.

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Biotic Factors - 4

• Disease
• Some organisms have learnt to survive by living
  off other animals.
• A parasite is an organism that lives in or on
  another organism causing it harm.
• Effect of Humans
• Human activities like industry, farming,
  forestry, roads and housing affect the habitats
  of other living things, as we compete for food,
  space and shelter.