Obj 2- Section A Flashcards
Ecology
the study of the interrelationships of living organisms with each other and with their environment.
Environment
the combination of factors that surround and act upon an organism
Biotic factors:
all the other living organisms that are present such as predators, prey, competitors, parasites and pathogens
Abiotic factors
Abiotic factors: all the non-living chemical and physical factors
Habitat:
the place where a particular organism lives.
For example, the habitat of an earthworm is the upper layers of the soil.
Species
a group of organisms of common ancestry that closely resemble each other and are normally capable of interbreeding to produce fertile offspring
Population:
all the members of a particular species living together in a particular habitat. For example, all the sea urchins living in a sea grass bed form a population.
Community
all the populations of different species living together in a particular habitat. For example, a woodland community consists of all the plants, animals and decomposers that inhabit the wood.
Ecosystem
a community of living organisms interacting with each other and with their abiotic environment
Niche
the position or role of an organism within an ecosystem. For example, an earthworm’s niche is to burrow through the soil, improving its aeration, drainage and fertility.
Why carry out an ecological study?
- identify diff species present
- where they live
- determine their numbers
- study relationships that they have with each other and with the abiotic factors
Why collect organisms?
-identify organisms
in which way can organisms be collected?
Pooters, pitfall traps, nets, plankton nets and a Tullgren funnel may be used
List the 4 sampling techniques
- Observations
- Quadrats
- Line transects
- Belt transects
Observation
The ecosystem should first be observed and the common species of plants and animals recorded. Any adaptations that enable the organisms to survive in the ecosystem should be noted, together
with any interrelationships between the organisms
Quadrat
- square frame with a known area
- placed at random several times
- num. of individuals of each species found within is counted.
- the quadrat can be made into a grid using string and the percentage of the quadrat area covered can be estimated.
Why do people use quadrats
Used to study the distribution and abundance of plants and stationary or slow moving animals in uniform ecosystems
Why do people use line transects
Line transects are useful where there is a transition of organisms across the ecosystem, e.g. down a rocky seashore. They give a quick idea of the species present and how they change across the ecosystem
How is a belt transect used?
made by placing two parallel line transects across an ecosystem. The species found between the lines are recorded. Alternatively, a quadrat
can be placed alongside one line transect and the number of individuals of each species found within its boundaries is counted. The quadrat is then moved along the line and counting is repeated at regular intervals.
How to find species density ( average number of individuals of a given species per m2)
tot. no. of species ÷ (area of quadrat x amount of quadrats used )
How to find the total population (total number of individuals of a given species in the area under study)
species density x tot. area of ecosystem studied
How to find the species cover ( percentage of ground covered by a given species)
(if quadrat is 1m2)
total percentage of ground that the species covered ÷ # of quadrats used
Species frequency
This is the percentage of quadrats in which the given species was found.
how does the recapture method work?
It is used to estimate the population size of moving animals (eg. sharks, sea turtles etc.) by collecting a sample of animals of the species and counting them, they are then marked (tag or paint) and released back into the same area and given time to mix with the original population.
A second sample is then collected, counted and the # of marked organisms counted
Formula for recapture method
marked organisms recaptured
organisms in 1st sample x # organisms in 2nd sample / # marked organisms recaptured
Why are abiotic factors important?
To determine the types and numbers of organisms that exist in a given environment, i.e they influence the distribution and behavior of living organisms
List the 3 abiotic factors
edaphic factors
climatic factors
aquatic factors
What are edaphic factors?
Those factors that are connected with soil
Describe soil
Soil is a mixture of inorganic rock particles, water, air, mineral salts, organic matter and living organisms such as plant roots, small animals and micro-organisms
What does soil provide organisms with?
Water, oxygen, nitrogen and mineral nutrients
Describe texture of soil
Texture i.e the composition of rock particles are formed from rocks by weathering and are classified by size eg. clay, silt, sand, gravel
Size of rock particles of certain types of soil:
Clay- less than 0.002mm
Silt- 0.002- 0.02 mm
Sand- 0.02-2mm
Gravel- greater than 2.0mm
What is the impact of soil texture on living organisms?
- Influences the water content of the soil (the smaller the soil particles, the more water held due to capillary and chemical forces ∴ the higher the water content
- Influences the air content of the soil (larger particles -> larger air spaces ∴ higher air content
- Influences the mineral ion content of the soil. (smaller the soil particles, the harder it is to leach) ∴ higher mineral content.
- Influences how easy it is for plant roots to penetrate and animals to burrow through the soil. The larger the particles, the easier to penetrate and burrow through.
How is water obtained and what does it do to the soil?
Obtained from rainfall and
held in a thin film around soil
particles by capillarity and
chemical forces.
Why is water essential to soil?
- Essential for photosynthesis in plants.
- Dissolves minerals so they can be absorbed by plant roots.
- Prevents the desiccation (drying out) of soil organisms without waterproof body coverings, e.g. earthworms.
Where is air present in soil?
Present in the spaces between the soil particles
Why is air important in soil?
- Oxygen in the air is essential for aerobic respiration in plant roots and soil organisms.
- Oxygen in the air is necessary for bacteria and fungi to decompose organic matter aerobically to form humus.
- Nitrogen in the air is necessary for nitrogen fixing bacteria to form
inorganic nitrogenous compounds, e.g. nitrates.
How are mineral nutrients in the soil formed?
Formed from decomposing
organic matter and by
dissolving from the
surrounding rock. Present as
ions dissolved in soil water
Why are mineral salts important in plants
essential for healthy growth
What is the optimum pH for most plants?
6.0 to 7.5
Why is pH important in soil?
Mainly affects mineral ion availability for plants. If the soil is too acidic or alkaline, mineral ions become less available.
Describe humus and how its formed
Formed by bacteria and fungi
decomposing dead or waste
organic matter. Humus is a
dark brown, sticky material
which coats soil particles,
mainly in the topsoil
What is the purpose of humus in soil?
- Improves the air content by binding soil particles together in small clumps called soil crumbs.
- Improves the mineral ion content by adding minerals, and absorbing and retaining minerals.
- Improves the water content by absorbing and retaining
List the climatic factors that affect terrestrial organisms
light, temperature, humidity, water
availability, wind and atmospheric gases.
List the aquatic factors that affect organisms in aquatic habitats
Aquatic organisms are affected by light, temperature, water availability and pollutants in the same way as terrestrial organisms. They are also affected by other factors.
