Paper 4 Higher Flashcards
How is carbon transferred between organisms in an ecosystem?
- carbon passed up the chain when animals eat plants and other animals
- and when microorganisms break down dead organisms
Describe the role of respiration in the carbon cycle
When organisms respire, carbon is returned to the atmosphere as carbon dioxide
Explain how microorganisms are involved in cycling materials through an ecosystem
- microorganisms (bacteria and fungi) break down dead organisms and the waste products of living organisms…
- which returns elements to the soil or air
- microorganisms also respire, which returns CO2 to the atmosphere
Why is it important that carbon is being constantly recycled in an ecosystem?
- Limited carbon in the world
- So it must be constantly recycled so there is enough for all the organisms in an ecosystem
- It’s an important element in the materials living things are made from
What is nitrogen fixation?
The process of turning nitrogen gas from the air into nitrogen compounds in the soil which plants can use
What type of bacteria turn ammonium ions into nitrates?
Nitrifying bacteria
Why can clouds form as warm air rises?
Water vapour in the air is carried upwards. When it gets higher up, it cools and condenses to form clouds.
Why do crops grow poorly on the same soil after years?
- crops remove nitrogen from soil as they grow
- they’re harvested before they die
- so decomposers and nitrifying bacteria can’t break down the nitrogen containing compounds
- so the nitrogen content of the soil falls
Apart from bacteria, name one other type of organism involved in decomposition
Fungi
How does drying food help to preserve it for longer?
Drying food removes the water that microorganisms need to survive, so it slows down decomposition
What is an ecosystem?
A community of organisms along with all the non-living (abiotic) conditions
What do plants need from their environment?
Light, space, water and minerals
What is the difference between a population and a community?
A population includes all the organisms of one species in a habitat, whereas a community includes all the organisms of different species in a habitat.
Why would trees being planted closely together mean very few plants grow below these trees?
The light intensity at the forest floor is likely to be very low because the sunlight is being blocked out by the densely packed pine trees. Without enough light, plants can’t photosynthesise, so they are unlikely to grow on the forest floor.
There will be a high competition with trees for nutrients and water from the soil, so there might not be enough to allow the growth of other plants.
What does it mean if two populations are interdependent?
They depend on each other to survive
Trophic level
Stage in a food chain
What kind of variation is plant height?
Continuous- it varies within a range and there are no distinct categories
Mutation
A rare, random change in an organisms DNA that can be inherited
How do mutations introduce genetic variants into populations?
They change the sequence of bases in DNA, which produces a generic variant
Outline what happens during meiosis
- cell duplicates genetic information
- cell divides twice, halving the genetic material at each division
- this produces four genetically different haploid gametes
How are offspring produced using asexual reproduction?
A cell divides by mitosis, resulting in two diploid daughter cells.
Which chromosomes does each sperm cell contain?
Either X or Y
Classification
The organisation of living organisms into groups
Artificial classification system
Sorts organisms into groups depending on observable features
Natural classification system
Uses information about organisms common ancestors and common structural features to sort organisms into groups
Molecular phylogenetics
Looking at an organisms molecules e.g. DNA to help determine the evolutionary history between groups of organisms
Killing People Could OF Got Somewhere
Kingdom, Phylum, Class, Order, Family, Genus, Species
Evolution
The change in inherited characteristics of a population over time, through the process of natural selection
Explain the process of natural selection
Some genetic variants give rise to phenotypes that are better suited to a particular environment, so organisms with these characteristics have an advantageous phenotype.
These individuals have a better chance of surviving and reproducing successfully, so the genetic variants responsible for the useful characteristics are more likely to be passed on to the next generation. Over many generations, the useful characteristics become more common in the population.
Explain how Darwin and Wallace’s ideas about evolution have influenced how living organisms are classified by biologists today
- led to the understanding that all life changes through the process of evolution
- and all living organisms have descended from a common ancestor
- biologists now classify organisms based on evolutionary relationships
What is a pitfall trap? What type of organisms is it used to collect?
A steep-sided container that is sunk in a hole in the ground with a partly open top. It is used to collect ground insects.
What is a Quadrat?
A square frame enclosing a known area
Give one assumption made when estimating population sizes using capture-recapture
There has not been a change in the population size between the samples
The marking hasn’t affected the individuals chance of survival
How are humans reducing the amount of land and resources that are available to plants and animals?
Building, farming, dumping waste and quarrying for metal ores
Local and global biodiversity
Local- the number of a species in the local area
Global- the number of a species on the entire planet
Suggest how rivers and lakes can become polluted and how this would reduce biodiversity
- waste products e.g. toxic chemicals/fertilisers can get into rivers/lakes
- this pollution kills plants and animals
- therefore it reduces biodiversity
Pesticide
A form of chemical pest control which kills the pests that damage crops and other plants
How can the use of fertilisers improve crop yield?
They replace missing elements from the soil which are important for growth and life processes, or to provide more of them.
