B3 - Life on Earth Flashcards Preview

GCSE OCR Biology > B3 - Life on Earth > Flashcards

Flashcards in B3 - Life on Earth Deck (28):

What is a species?

Similar organisms capable of breeding together to produce fertile offspring.


How is a cactus adapted to its desert environment?

  • It has leaves reduced to spines, to cut down water loss.
  • A thick outer layer, to cut down water loss.
  • A deep, wide-spreading root system to obtain as much water as possible.


What natural (Not humanly affected) environmental problems can cause species to become extinct?

  • Increased competition.
  • New predators.
  • New diseases.
  • Availability of prey (e.g: Due to environmental changes such as low rainfall decreasing the amount of lettuce, and causing reductions in slug numbers).


What is an ecosystem?

An area containing a self-sustained community of organisms.


What is an autotroph?

An autotroph is a self-feeder (It makes its own food). They are also known as producers.


What is a heterotroph?

An organism which gets its energy by consuming other organisms. Also known as a consumer.


What is a herbivore?

A heterotroph which eats plants.

They are primary consumers.


What is a carnivore?

A heterotroph which eats other animals.

They are secondary or teriary consumers.


What is a detritivore?

Be careful with your spelling here as well!

A heterotroph which obtains nutrients by consuming detritus (Decomposing plant and animal parts, as well as faeces).


Why is not 100% of energy passed on to species further down in the food chain?


  • Some energy is lost through heat or respiration.
  • Some energy is excreted as waste products.
  • Some energy is trapped in materials such as bone and fur.
  • Some species don't eat the entirety of the animal.
  • Some species share food.


This also means that less energy is available at each stage of energy transfer, and there's a limit to the length of a food chain.


Draw the Nitrogen Cycle.

A image thumb

Where can nitrogen-fixing bacteria be found?

  • In soils.
  • In root nodules of plants like clover and beans (leguminous plants).


What is the process called where nitrates are broken down into nitrogen by bacteria in the soil?



Draw the Carbon Cycle.

A image thumb

What are the two ways which we can measure Environmental Change?

  • Using metres to measure levels of oxygen, carbon dioxide, nitrates, temperature, etc.
  • Using living organisms as indicators. For example, mayfly larvae in rivers need high oxygen levels so, if there is lots of them, the level of pollution is low (Pollution reduces the amount of oxygen). Others include lichens (Which don't grow if the air is polluted) and phytoplankton.


How did the very first microorganisms come about on Earth?

It was debated whether the conditions or an external source (e.g: A comet) caused them to form.

However, experiments have simulated the harsh conditions on Earth millions of years ago, which led to simple organic molecules developing.


What are the conditions required for decay?

Oxygen or moisture are required for decay.


What sources of evidence support the fact that all living organisms share a common ancestor?

  • The fossil record (Older fossils found at bottom and there is a gradual change from bottom to top).
  • DNA evidence (All species are related, as we all have DNA, with similarities and differences. Chimpanzees are our closest genetic relative, and share 98.8% of DNA with us).


Name an example of a species which has undergone change via Natural Selection.

The Pale Peppered Moth has evolved to become Dark Peppered Moths since the Industrial Revolution.


-- Finish me - Page 33 of Revision Guide. Extinctions causes directly/indirectly by man --


Only thing you need to know for now is that extinctions can be good (Irradicating viruses) or bad (Irradicating an animal species).

-- Rate me 5 --


What is biodiversity?

The variety of life that exists on Earth.


Variety is important because without it, people would start to run out of food crops and medicines. There are potentially many medicines in areas like the Amazon rainforest - an area rapidly undergoing deforestation.


-- Finish me - Page 34 of Revision Guide - Sustaining Biodiversity --

-- Rate 5 --


If there is lots of mayfly nymphs found in one area, then the pollution levels are high/low?

If there is lots of mayfly nymphs found in one area, then the pollution levels are low.


What is meant by sustainability?

Meeting the needs of the people today without damaging the Earth for future generations.


Gerbils are adapted to living in deserts and feed on plants.


They can go for long periods of time without drinking water.


Suggest how the gerbil manages to survive on so little water.

  • Absorbs water from plants it eats.
  • Absorbs water through respiration.
  • No sweat glands.
  • Stores water.
  • More ADH.
  • Nocturnal (Most active at night).
  • More concentrated/smaller volume of urine.
  • Dry faecaes/reabsorption of water in colon.


What is the difference between perceived and calculated risk?

Perceived risk is subjective.

Calculated risk uses data.


Give 2 reasons why not all food webs are closed loop systems.

  • Other organisms will interact with the food web.
  • Migration.


Why must microorganisms reproduce rapidly?

  • To quickly take advantage of food/competition.
  • Decomposition rate can be enhanced.
  • Microorganisms are very small relative to animals/plants.