Biology Higher 4 GCSE (only B4 and B5) Flashcards
define an ecosystem
the living and physical conditions in an area
define a community
the organisms within an ecosystem
define a habitat
the area in which a community lives
define population
the total number of organisms in an area
producers
plants and organisms that can make up their own food.
consumers
they are unable to make their own food and have to eat producers to gain energy
decomposers
they gain energy by breaking down dead or decaying material.
biotic factors
living factors
like number of trees, squirrels etc.
abiotic factors
non-living factors
like light intensity, temperature, pH, moisture level.
what is competition
when animals compete fr limited resources
what do animals need
food water breeding partner space shelter
what do plants need
light water carbon dioxide minerals space
3 types of interdependance
predation
mutualism
parasitism
how may energy be lost between trophic levels
not all of the organism is eaten
some of the biomass may be used in respiration, which produces ATP for movement and heat
Indigestible parts of an animal- hair, nails
waste products
efficiency of biomass transfer
efficiency of biomass transfer=
biomass after transfer/ biomass before transfer *100
how does nitrogen go from the air to plants
nitrogen-fixing bacteria that mix oxygen with nitrogen in the air to make nitrates
how does ammonia in the soil get absorbed by plants
nitrifying bacteria turns ammonia into nitrates
how do nitrates turn back into nitrogen in the atmosphere
denitrifying bacteria releases nitrogen
what is percolation
when water trickles through soils and rocks to join the river
why do the levels of carbon dioxide vary during the day
photosynthesis only takes place during the day- so co2 in only removed during the daylight
respiration happens 24/7 so co2 is continued to be added the entire day
whats the difference between a decomposer and a detritivore
decomposers are microorganisms. they break down or decay organic material at a microscopic level.
detritivores are small animals that speed up decomposition by breaking down organic material into smaller pieces.
how do bacteria release nutrients
they release enzymes on the dead remains
the enzymes can then digest the dead matter and make it soluble (dissolve-able)
the soluble products are absorbed by the fungus
what factors affect the rate of decomposition
warm temperatures
Moist environments: needs water to decompose
aerobic conditions: oxygen is needed for the microorganisms to respire.
rate of decay
rate of decay = change in mass (g)/ time (day)
phenotype
the appearance of an organism
what is variation
difference within a species
genetic variation and environmental variation
genetic- physical genetic material in an organism (dna)
environmental- the environment in which you live in
discontinuous variation
individuals that show characteristics that fall into distinct groups, such as blood groups
continuous variation
can have any value between minimum and maximum
asexual reproduction
usually produces clones examples: potato plants spider plants daffodils
sexual reproduction
requires 2 parents
its offspring isn’t identical since it uses 2 pair of genes
it produces sex cells called gametes that fuse together in fertilisation.
advantages and disadvantages of asexual reproduction
advatages:
if the parent can adapt well to an area, so can the offspring
only one parent is needed- so its quicker to reproduce
disadvantage:
if there is a change to biotic or abiotic changes, it may destroy the entire species
advantages and disadvantages of sexual reproduction
advantage:
variation in offspring leads to adaptations in a species
disadvantage:
reproduction requires 2 parents. It is much slower so fewer offspring are produced
differences between diploid and haploid cells
diploid: 46 chromosomes
haploid: 23 chromosomes
what is a zygote
a fertilised egg cell
meiosis
produces gametes
which are haploid cells (23)
chromosomes for male
XY
chromosomes for female
XX
history of genetics
1866- Gregor Mendel carried out an experiment on peas
He noticed that characteristics were determined by hereditary units (now called genes)
They are passed on from both parents and they are either dominant or recessive
1869- Nuclein discovered
Friedrich Miescher discovered there is an acidic substance present in each nucleus (DNA)
1944- Genes can be transferred from one generation to another
1950- DNA base pairs found by Erwin Chargaff
1952- DNA crystals photographed by Maurice Wilkins and Rosalind Franklin
1953- Double helix structure
James Watson and Francis Crick
1953- 2000 - Identified individual genes that code for genetically inherited disorders
2003- Human genome project completed- they discovered 24000 genes
evolution
a gradual change in species over time
explain natural selection
- Organisms show variation caused by a difference in their genes
- The organisms with the characteristics that are best adapted will survive
- genes from the successful will be passed down to their offspring
- the process is then repeated many times
examples of evolution
peppered moths-
before the industrial revolution, moths were pale. then a mutation made them dark coloured, but they didn’t survive because they couldn’t camouflage against the light coloured trees
after the industrial revolution, the trees were covered in soot so they became dark and the darker moths became more camouflaged against them, so they survived longer
how are fossils made
- the reptile dies
- the flesh rots, leaving the skeleton covered in sand and soil before it is damaged
- protected over millions of years, it becomes mineralised and turns to rock
- eventually, the fossils emerge as the rocks move and erosion takes place
how does the fossil record provide evidence for evolution
fossils of the simple organisms are generally much older compared to the more complex ones that are much younger
plant fossils appear before animal ones- so animals clearly needed plants
closely related organisms came from the same ancestor and this can be found by studying their anatomy
what other evidence is there for evolution
rapid change in species- as bacteria can replicate, scientists can study evolution in action and observe the changes
extinction- species that are unable to adapt to environmental changes usually die out
molecular comparison- scientists have began to compare the DNA and proteins of different species and the order of nucleic orders etc.
Theory of evolution
He joined a scientific expedition to the Galapogas Islands and he made his observation on finches. He saw that the beaks of the finches was entirely based on the types of food that they ate.
At the same time that Charles Darwin was developing his theory, Alfred Russel Wallace gathered evidence for his theory, which was overall very similar to Darwin’s so they did a joint report.
Binomial nomenclature
A universal system of naming species.
The first name is the organism’s genus.
The second name is the organism’s actual name
Classification system
Kingdom Phylum Class Order Family Genus Species
Natural classification
looking for a common ancestor. the study of evolutionary links is known as phylogeny.
artificial classification
they group together organisms based off of their physical, observable characteristics.
define a species
a group of organisms that share the same genetic material and can breed to have fertile offspring
A research team want to genetically engineer pigs so that they produce organs that are not
rejected by humans.
Describe how they could do this
Identify gene for human tissue types isolate this gene insert this gene into the pig embryo replicate the gene check the cell for expression of the gene
how is malaria spread
an example of protozoa
mosquitoes suck blood out of someone with malaria
then pass it on
what happens to a person’s lungs when they are having an asthma attack
airways become swollen and restrict air flow.
muscles around bronchiols contract
why is the ozone layer reducing
people using CFCs, refrigeration
greenhouse gases increased
