7 - Ecology

• What is a 'habitat'?

  - the environment in which an organism lives
• What is a 'population'?

  - the total number of organisms of the same species living in the same geographical area
• What is a 'community'?

  - the populations of all of the different species that live in the same habitat
• What is an 'ecosystem'?

  - the interaction of a community of biotic parts with the abiotic parts of their environment
• What is the difference between 'biotic' and 'abiotic'?

  biotic = living organisms

  abiotic = non-living parts
• What do organisms need to survive and reproduce?

  - organisms require a supply of materials from their surroundings and from the other living organisms there
• What 4 main factors do plants in a community or habitat often compete for?

  - light

  - space

  - water

  - mineral ions
• What 4 main factors do animals often compete with each other for?

  - food

  - water

  - mates

  - territory
• What is the term for how within a community, each species depends on other species for certain things; if one species is removed, it can affect the whole community?

  interdependence
• What makes a community be stable?


  - a stable community is one where all the species and environmental factors are in balance => population sizes remain fairly constant
• Give 4 examples of factors that species depend on other species for?

  - food (eg. lions depend on gazelles to eat)

  - shelter (eg. animals may depend on trees to provide shelter from the Sun)

  - pollination (eg. flowers depend on bees)

  - seed dispersal (eg. flowers depend on birds to disperse seeds in their faeces)

  
• How would a change in the availability of food affect organisms in a community?

  - availability of food falls => the populations of species would also fall as they have less food to eat => less likely to survive and live on to reproduce

  - availability of food increases => the populations of species would also increase
• How would the arrival of a new predator affect organisms in a community?

  => population of a prey species will fall

  => more competition for existing predators that eat the same food as the new predator => less food
• How does the level of competition affect organisms in a community?

  - if a species is outcompeted, its population can fall => may even become extinct if numbers are insufficient to breed
• How would the arrival of new pathogens affect organisms in a community?

  - if an infectious disease emerges and spreads, it can wipe out a population of a species
• How does changing light intensity affect plants?

  - if the light intensity is too low, the rate of photsynthesis falls => plants will grow more slowly => animals may not have enough food
• How does changing temperature affect plants?

  - if temperature changes significantly, the distribution of a species may change (eg. animals could migrate or plant species may disappear from that area)
• How do moisture levels affect organisms in a community?

  - both plants and animals need water to survive => if there are low levels of moisture, plants that are not adapted may die
• How does soil affect plants?

  - many plants cannot grow on soil which is too acidic or too alkaline

  - plants also need certain mineral from the soil
• How does wind intensity and direction affect plants?

  - stronger winds may cause plants to lose water via transpiration
• How do the carbon dioxide levels affect plants?

  - a higher carbon dioxide concentration means plants can photosynthesise more
• How do the oxygen levels in water affect aquatic animals?

  - aquatic animals need dissolved oxygen from the water for respiration
• What is the difference between the 3 types of adaptations?

  - structural adaptations relate to the physical body shape or body structure

  - functional adaptations relate to the body functions of an organism

  - behavioural adapatations relate to the animal's lifestyle or behaviour (things that the animal does)
• How are camels STRUCTURALLY adapted to the hot and dry conditions of a desert?

  - camels have a hump on their back which is a store of fat, a thermal insulator (by storing the fat in one place, this allows heat loss from the other parts of the camel's body => reduces water loss from sweating) + metabolic reactions can be used to produce water from the fat

  - thick coat on the upper surface of their body => insulates the top of the camel from the heat of the Sun => reduces water loss from sweating

  - the inside of a camel's mouth is leathery => allows camel to shew desert plants (which often have thorns)

  - camels have long eyelashes => keep dust out of their eyes

  - camels can close their nostrils => keep dust out of their nose

  - camels have wide feet => prevents the camel from sinking into the sand

  
• How are camels FUNCTIONALLY adapted to the hot and dry conditions of a desert?

  - camels produce CONCENTRATED URINE and DRY FAECES => reduce water loss

  - camels can tolerate very large changes in their body temperature => helps them to cope with the intense heat of the desert

  
• What are different ways that some animals BEHAVIOURALLY adapted to survive in both hot and cool conditions?

  - some animals are NOCTURNAL (mainly active at night when it is cooler) => avoid the heat of the daytime + these animals may also live in burrows underground during the day => keep cool and protects them from predators

  - some animals, eg. polar bears, hibernate during the winter to avoid the cold (the animal becomes inactive and all the body processes slow down)

  - some animals, eg. some birds, migrate south to warmer climates

  
• How are some animals STRUCTURALLY adapted to survive the cold climate?

  - very thick fur => provides insulation and reduces heat loss to the air

  - fur on the soles of their feet, eg. the Arctic fox => reduces heat loss to the ice and the snow

  - very small ears => reduces the overall surface area of the animal, eg. the Arctic fox => reducing heat loss

  - white coat => effective camouflage (helps the animal to hunt its prey)

  
• How are cacti adapted to live in the dry desert?

  - very small leaves => reduce surface area for water loss (or even no leaves at all, only spines which also protect the cacti from animals)

  - extensive and shallow roots => absorb maximum water after rainfall

  - cacti can store water in their stems => survive many months without rain
• What are 'extremophiles'?


  - organisms that live in environments with extreme conditions, eg. bacteria that live in deep sea vents

  
• Give 3 examples of extreme conditions that an extremophile may be able to survive in?

  - high temperature

  - high pressure

  - high salt concentration
• What do food chains represent?

  - feeding relationships within a community
• What do all food chains begin with?

  - all food chains begin with a PRODUCER which synthesise complex molecules (biomass)

  - this is usually a green plant or alga which makes glucose by photosynthesis
• What is the general food chain?

  producer => primary consumer (prey) => secondary consumer => tertiarry consumer => apex predator
• Explain this predator-prey cycle graph.

  - prey population increases => more food for predators => predator population increases => more of the prey are eaten => prey population falls => less food for predators => predator population decreases => prey population increases

  - only true in a stable community

  
• What are transects and quadrats used for?

  - a range of experimental methods using transects and quadrats are used by ecologists to determine the distribution and abundance of species in an ecosystem
• What is random sampling used for?

  
  

  How is random sampling done? What is a quadrat?

  
  

  What can we sample with this method?

  - used to compare the numbers of organisms in different areas

  
  

  - by using a quadrat (a wooden/plastic square)

  - we throw the quadrat randomly and then count the number of organisms inside wherever it lands

  
  

  => we can use random sampling to sample plants or slow-moving animals

  
• How can we increase the validity of random sampling?

  - throwing the quadrat a large number of times
• How can we increase the accuracy of random sampling?

  - using a smaller quadrat
• In random sampling, what is the equation to estimate the total population size of a species?

  (total area / area sampled) x number of organisms of that species counted in sample
• What is sampling along a transect used for?

  
  

  What is a transect? How is sampling along a transect done?

  - to investigate how the numbers of species change as we move across a habitat

  
  

  - a transect is simply a line (eg. a tape measure of a piece of rope)

  - we use a quadrat to count the organisms at intervals on the transect