B3 - Life on Earth Flashcards
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?
Because…
- 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.
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?
Denitrification.
Draw the Carbon Cycle.
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.
