4th Form Definitions and Key Concepts Flashcards
1
Q
diffusion
A
the net movement of substances from an area of high to low concentration, down a concentration gradient and can be across a partially permeable membrane
2
Q
osmosis
A
the net movement of water from an area of high to low water potential, down a water potential gradient and can be across a partially permeable membrane
3
Q
active transport
A
the movement of substances from an area of low to high concentration, against a concentration gradient, using the energy from ATP
4
Q
phloem
A
a tissue in plants that is specialised to transport sugars and amino acids both up and down the plant from the leaves to respiring tissues. this is called translocation
5
Q
translocation
A
the movement of sugars and amino acids through the phloem
6
Q
transpiration
A
water loss via evaporation through the stomata in the leaves down a water potential gradient
7
Q
transpiration stream
A
the upwards movement of water through the xylem from roots to leaves
8
Q
xylem
A
a tissue that is specialised to transport water from the roots to the leaves. Is dead and hollow to allow the continuous column of water
9
Q
antidiurectic hormone (ADH)
A
a hormone produced by the pituitary gland that increases the reabsorption of water in the collecting duct of the kidney
10
Q
bladder
A
the organ that collects and holds urine before it is excreted
11
Q
Bowman’s capsule
A
structure at the start of the nephron where the glomerular filtrate enters from the glomerulus and connects to the proximal convoluted tubule
12
Q
collecting duct
A
final part of the nephron which connects to the ureter where water is reabsorbed, how much is determined by its permeability which is controlled by ADH
13
Q
convoluted tubules
A
tubes in the nephron (PCT and DCT) where the filtrate flows through, substances (glucose, ions, amino acids) from the filtrate are reabsorbed by active transport into the blood from these tubes
14
Q
excretion
A
the removal of metabolic waste from the body (co2 for example)
15
Q
glomerulus
A
a bundle of capillaries where ultrafiltration occurs
16
Q
loop of henle
A
part of the nephron after the PCT where water and salts are reabsorbed
17
Q
nephron
A
functional unit of the kidney that contains the bowman’s capsule, PCT, Loop of Henle, DCT and collecting duct
18
Q
organs of excretion
A
any organ that removes metabolic waste, the lungs removing carbon dioxide and water vapour produced from respiration, the kidneys removing water, urea and salts and the skin excreting water and salts
19
Q
osmoregulation
A
regulation of the volume of water in body fluids by the use of the hormone ADH
20
Q
selective reabsorption
A
the selective uptake of useful substances such as glucose, water and ions back into the blood from the nephron. selective reabsorption in the PCT involves the active transport of glucose out of the PCT back into the blood
21
Q
stomata
A
small holes found in the lower epidermis that open and close thanks to the guard cells. control the loss of water by closing during the night but open during the day thanks to the guard cells to allow the diffusion of carbon dioxide and oxygen
22
Q
ultrafiltration
A
the filtration of blood at the glomerulus under high pressure to form the glomerular filtrate. contains water, ions, glucose, urea and other molecules. does not contain proteins and blood cells as they are too large and cannot leave due to the basement membrane
23
Q
ureter
A
tubes that carry urine from the kidneys to the bladder
24
Q
urethra
A
tube that carries urine from the bladder out of the body
25
urine
waste product of the kidney that contains water, urea and ions
26
follicle stimulating hormone (FSH)
a hormone produced by the pituitary gland that stimulates the growth of follicles in the ovary and stimulates the release of oestrogen
27
luteinising hormone (LH)
a hormone secreted by the pituitary gland that stimulates ovulation (the release of an egg from the ovary) and the release of progesterone
28
progesterone
a hormone produced in the ovaries, specifically by the corpus luteum and the placenta that maintains the uterus lining and inhibits the release of FSH and LH
29
amniotic fluid
the fluid that surrounds and protects the embryo from bumps and sudden changes from the mother in the uterus
30
asexual reproduction
a form of reproduction involving a single parent CELL. it created genetically identical offspring which have survival value in a stable environment. usually producing large numbers of offspring and quickly
31
cuttings
method of cloning plants. a section of the stem is cut, with at least one leaf, from a parent plant that you want to clone and is replanted in damp compost with hormones that stimulate root growth (auxins)
32
embryo
an unborn organism in an early stage of development formed by mitosis
33
fertilisation
the fusion of the nucleus of a male and female gametes to form a diploid zygote
34
gametes
sex cells, sperm in males and egg cells in females, each being haploid (half the number of chromosomes). Pollen is the male gamete of a plant
35
germination
seeds need oxygen (for respiration), warmth (for enzymes), water (activate enzymes) to germinate. this occurs until photosynthesis can take place in the leaves, then germination has finished.
36
menstrual cycle
a monthly cycle in women that involves the growth of the uterus lining, release of an egg, maintenance of the uterus lining and then its shedding
37
meiosis
a form of cellular division that produces gametes, genetically different, haploid cells. 4 daughter cells produced over two divisions involving two parent CELLS only occurs in the reproductive organs and used to produced gametes
38
mitosis
a form of cellular division that produces two genetically identical, diploid cells from a single parent CELL. 2 daughter cells produced over one division, occurs everywhere in the body and used for the growth and repair of cells/tissues
39
monohybrid cross
a cross between two organisms that is used to investigate the inheritance of a single gene
40
oestogen
female reproductive hormone that causes the uterus lining to develop. It inhibits FSH. also responsible for the development of the secondary sexual characteristics
41
placenta
attached to the uterus lining during pregnancy. acts as an exchange surface between the mother and foetal blood where glucose (for respiration), amino acids (for protein synthesis) and oxygen (for respiration) diffuse into the foetal blood and waste products like carbon dioxide and urea diffuse into the mother’s blood. also produces progesterone
42
pollination
transfer of pollen grains (either by wind or insects) from the anther to the stigma, where fertilisation occurs. can be self-pollination (same flower) or cross pollination (flowers on different plants). also wind or insect pollination
43
wind pollinating flowers
exposed stigma and stamen, dull/colourless flowers, no nectar, small and smooth pollen grains, feathery stigma
44
insect pollinating flowers
enclosed stigma and stamen, large, colourful petals with nectar present, stigma is sticky and large, sticky pollen grains
45
secondary sexual characteristics
features that appear during puberty and differ between genders. examples; voice changing, growth of hair, development of breasts, hips widening, growth of male reproductive organs, start of menstrual cycle
46
sexual reproduction
a form of reproduction that involves the fusion of male and female gametes, creating genetic variation in the offspring and has survival value in a changing environment. involves two parent CELLS
47
testosterone
the main male reproductive hormone, produced by the testes, stimulates sperm production (along with FSH) and responsible for the development of male secondary sexual characteristics
48
zygote
a fertilised egg cell (diploid)
49
allele
an alternative version of a gene that cause difference in inherited characteristics such as hair colour
50
chromosome
a long, coiled molecule of DNA that carries genetic information in the form of genes
51
codominance
two different alleles both being expressed in the phenotype
52
deoxyribonucleic acid (DNA)
double stranded polymer arranged in a double helix, made up of DNA nucleotides that carry the genetic code. there are 4 DNA nucleotides, each made up of a phosphate molecule and a deoxyribose sugar but differ due to their nitrogenous base, adenine, thymine, cytosine and guanine
53
dominant
the allele that is always expressed in the phenotype when in the genotype, denoted by a capital letter
54
evolution
the change in inherited traits within a population over time. modelled by natural selection
55
gene
a section of DNA that codes for a specific sequence of amino acids that forms a protein and is responsible for a particular trait (phenotype)
56
genome
the complete genetic material of an organism
57
genotype
all of the alleles present in an organism
58
haploid
a cell that contains half the amount of genetic information. Human gametes have 23 chromosomes (it only contains 1 chromosome of each homologous pair)
59
heterozygous
when an organism has two different alleles of a gene, e.g. Gg
60
homozygous
when an organism has two of the same alleles, e.g. GG/gg
61
mutagens
chemicals that increase the frequency of mutations in DNA
62
mutation
a random change in DNA which may result in genetic variations that can produce a slightly different protein and therefore a different phenotype if the mutation occurs in a gene. examples being addition, substitution and deletion
63
natural selection
a change in the environment (selection pressure) causes an organism with a mutated allele to be at an advantage, they are more likely to survive, reproduce and pass on their advantageous, mutated allele to their offspring. this happens over many generations and results in the mutated allele becoming more frequent in the population at the expense of the previously dominant allele
64
nucleus
an organelle found in most eukaryotic cells that contain the genetic material of the cell and controls the activities of the cell
65
phenotype
an organisms visual characteristics due to the organism’s genotype and interactions with the environment. e.g. hair colour
66
recessive
an allele that is only expressed in the phenotype when present with another recessive allele in the genotype (homozygous). Denoted by a lower case letter, e.g. q
67
sex chromosomes
a pair of chromosomes that determine the sex of an individual. In humans this is the 23rd pair and is XX in females and XY in males
68
variation
the differences between individuals due to genes, the environment or a combination of both
69
abiotic factors
non-living parts of an ecosystem, e.g. temperature, light intensity, moisture, wind speed, soil pH, mineral concentration, carbon dioxide and oxygen levels
70
biodiversity
variety of living organisms in an ecosystem. It takes into account the number of different species and the population of each
71
biotic factors
living components of an ecosystem, e.g. food availability, pathogens, predation and competition (interspecific competition – competition between members of different species and intraspecific competition – competition between members of the same species)
72
community
all the populations of different species living together in a particular place at a particular time
73
distribution
spread of living organisms in an ecosystem, affected by environment changes
74
ecosystem
the community of organisms (biotic) and non-living components (abiotic) of a particular area and how they interact with one another
75
habitat
the place in an ecosystem when an organism lives
76
population
all the organisms of the same species living with one another in a habitat at any one time
77
decomposers
organisms that release enzymes which speed up the breakdown of dead plant and animal material, e.g. bacteria and fungi
78
decomposition
the breakdown of dead materials into simpler organic matter that can eventually be absorbed by plants. the rate at which it occurs is affected by temperature, water and oxygen content
79
energy transfers
the flow of energy from one trophic level to the next. Is never 100% and decreases the further you move up the food chain due to not all of the organism being eaten, not all of it being digested, some of the energy being used in respiration/movement of the organism and some energy being lost in the excretory products
80
food chain
shows the feeding relationships between organisms and the stages of biomass transfer. the arrows represent the flow of energy between organisms
81
food web
network of food chains that shows how energy can flow in different ways and that animals can feed on more than one organism
82
primary consumer
herbivores that consume producers in a food chain
83
producers
photosynthetic organisms at the start of the food chain that provide biomass for all the organisms in the food chain
84
pyramid of biomass
a pyramid, with each layer of the pyramid representing the amount of mass of living material at each trophic level of a food chain. When asked to draw one in exams, they often start off bigger at the bottom and get smaller at each level above
85
pyramid of number
a pyramid showing the numbers of each organisms at each trophic level, often looking similar to the pyramid above but if the producer is large and small in number, like a tree, can look quite different
86
quadrat
a square grid used to sample populations and to determine abundance and distribution of organisms in an ecosystem
87
quaternary consumers
carnivores that consume tertiary consumers
88
secondary consumers
carnivores that consume primary consumers
89
teritary consumers
carnivores that consume secondary consumers
90
top carnivore/apex predator
an organism in a food chain/web that is not consumed by another
91
trophic level
the position of an organism in a food chain. only around 10% of the energy is transferred from one level to the next
92
carbon cycle
the cycle where carbon moves between organisms and the environment, namely in the form of carbon dioxide and involving respiration, photosynthesis, fossilisation and combustion
93
decomposers in the nitrogen cycle
organisms that release enzymes that catalyse the breakdown of dead plant and animal material releasing nitrogen containing compounds such as ammonia into the soil
94
denitrifying bacteria
bacteria that convert nitrates in the soil into nitrogen gas. occurs when conditions are anaerobic and can be prevented by ploughing the soil to aerate the soil and having good drainage to prevent the air spaces from filling with water, both ensuring there is adequate amounts of oxygen to prevent the growth of these organisms
95
nitrifying bacteria
aerobic organisms that convert ammonia to nitrites and then nitrates which can be absorbed by plants using active transport in the roots
96
nitrogen cycle
the cycle through which nitrogen moves between living organisms and the environment
97
nitrogen fixing bacteria
bacteria that convert nitrogen gas into nitrogen containing compounds that plants can use. can be free living in the soil or found in root nodules of leguminous plants (clover, peas) where they have a mutualistic relationship and convert nitrogen gas to nitrogen containing compounds which the plant receives and in return get sugars from the plant that have been produced via photosynthesis
98
deforestation
removal of trees to use the resources on the tree for fuel or for space that the trees occupy
99
eutrophication
pollution of water by fertilisers being added in nearby land and nutrients leaching into the water causing excessive growth of algae at the surface of the water (algal bloom), which prevents light reaching photosynthetic plants at the bottom of the water, causing them to die, reducing the oxygen levels in the water and eventually resulting in the death of all aerobic organisms in the water
100
global warming
rise in average temperatures on earth due to increased levels of greenhouse gases like carbon dioxide, causing the enhanced greenhouse effect where more heat is trapped in the atmosphere and once reflected off the surface is reflected back to the surface rather than escaping
101
greenhouse gases
gases in the earth’s atmosphere that trap heat and cause the greenhouse effect, examples being water vapour, carbon dioxide, methane, nitrous oxide and CFCs
102
leaching
movement of nutrients e.g nitrates in the soil into lakes and rivers due to rain and can lead to eutrophication
103
pollution
contamination or destruction of the environment due to human impacts
104
biological control of pests
use of other species to kill pests, e.g. hawks to control the rat population
105
interspecific predation
where an organism of one species kills an organism of a different species, e.g. in fish farming one species of fish killing another species of fish for food in the same tank. this can be reduced by separating fish of different species into separate tanks
106
intraspecific predation
where an organism of one species kills an organism of the same species. In fish farming this can be reduced by separating fish by age and size in different tanks
107
lactobacillus
a bacterial species used to make yoghurt
108
pesticides
chemicals used to kill pests. can be split into herbicides which are used to kill weeds and insecticides which are used to kill insects
109
yeast
unicellular fungi used to produce bread. they anaerobically respire to produce carbon dioxide which makes the bread rise and the ethanol which is also produced evaporates when the bread is heated
110
selective breeding
process where organisms with desirable characteristics are selected to breed and produce offspring with the desirable characteristics. can be used for both plants and animals
