Ecology

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

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).

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.

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.

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.

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.

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.

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.

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.

Ecological Pyramids Food chains indicate what eats what, but doesn’t 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)

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.

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.

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.

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:

Climatic Factors – 2 Light Temperature Air (oxygen) Water (rain fall etc) Humidity Wind Topography (angle, aspect and altitude)

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.

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 < 0.002mm Silt 0.002 to 0.06mm Sand 0.06 to 2.0mm

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.

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.

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.

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

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.

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.

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.

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.