Biology Paper 2 GCSE Flashcards
(165 cards)
1
Q
What is Homeostasis?
A
The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to external and internal changes
2
Q
What does Homeostasis do?
A
maintains optimal conditions for enzyme action and all cell functions
3
Q
Homeostasis contains control of what 3 things?
A
Blood glucose concentration
body temperature
water levels
4
Q
All control systems include what?
A
- Cells called receptors
- coordination centers
- effectors
5
Q
What do receptors do?
A
detect stimuli (changes in the environment)
6
Q
What is an example of a coordination centre and what do they do?
A
brain, spinal cord, pancreas
They receive and process information from receptors
7
Q
What do effectors do?
A
muscles or glands, which bring about responses which restore optimum levels
8
Q
What do nervous systems do?
A
enables humans to react to their surrondings and to coordinate their behaviour
9
Q
How does the nervous system work?
A
information from receptors passes along cells (neurones) as electrical impulses to the central nervous system. The CNS is the brain and spinal cord. The CNS coordinates the response of effectors which may be muscles contracting or glands secreting hormones
10
Q
What is a synapse?
A
a junction between two nerve cells, consisting of a minute gap across which impulses pass by diffusion of a neurotransmitter.
11
Q
What does sensory neurones do?
A
carry signals from receptors to the spinal cord and brain.
12
Q
What does a relay neurone do?
A
carry messages from one part of the CNS to another.
13
Q
What do motor neurones do?
A
carry signals from the CNS to effectors.
14
Q
What is the endocrine system?
A
composed of glands which secrete chemicals hormones directly into the bloodstream. The blood carries the hormone to a target organ where it produces an effect
15
Q
What is the pituitary gland?
A
a ‘master gland’ which secretes several hormones into the blood in response to body conditions. These hormones in turn act on other glands to stimulate other hormones to be released to bring about effects.
16
Q
How is blood glucose concentration monitored and controlled?
A
Pancreas
17
Q
If the blood glucose concentration is too high what does the pancreas do?
A
pancreas produces the hormone insulin that causes glucose to move from the blood into the cells and glucose is converted to glycogen in liver
18
Q
In liver and muscle cells excess glucose is converted to what?
A
glycogen for storage
19
Q
What is Type 1 diabetes?
A
disorder in which the pancreas fails to produce sufficient insulin. It is characterised by uncontrolled high blood glucose levels and is normally treated with insulin injections
20
Q
What is Type 2 diabetes?
A
the body cells no longer respond to insulin produced by the pancreas. A carbohydrate controlled diet and an exercise regime are common treatments. Obesity is a risk factor for Type 2 diabetes
21
Q
If the blood glucose concentration is too low what does the pancreas do?
A
the pancreas releases glucagon. The glycogen is broken down to glucose and amino acids/fats are broken down
22
Q
What is the post-synaptic neurone?
A
neurone after the synpase
23
Q
What is the neurotransmitter?
A
a type of chemical released by the neurone
24
Q
How do nerve impulses travel from one neurone to the next?
A
- A chemical called a neuronetransmitter is released from the presynaptic neurone.
- The neuronetransmitter diffuse across the synpase.
- The neurotransmitter bind to the receptors on the post-synaptic neurone causing a new impulse to be sent along the post-synaptic neurone
- the neurotransmitters diffuse back across the synapse and are absorbed by the pre-synaptic neurone to be used again
25
What is reaction time?
time between the presentation of a stimulus and the imtiation of the muscular response to that stimuli
26
How is glucose controlled using negative feedback control?
Blood glucose is controlled by the liver. When the blood glucose level is too high insulin is released and glucose is taken in by cells. Then if the blood glucose gets too low glycogen is released and is broken down into glucose. Insulin allows glucose to move from your blood into your cells where its used for respiration. Excess glucose is converted into glycogen and stored in the liver and muscle cells. Glycogen is insoluble and can be converted back into glucose
27
How is glucose controlled using negative feedback control?
Blood glucose is controlled by the liver. When the blood glucose level is too high insulin is released and glucose is taken in by cells. Then if the blood glucose gets too low glycogen is released and is broken down into glucose. Insulin allows glucose to move from your blood into your cells where its used for respiration. Excess glucose is converted into glycogen and stored in the liver and muscle cells. Glycogen is insoluble and can be converted back into glucose
28
What is Oestrogen?
Main female reproductive hormone produced in the ovaries. It causes the lining of the uterus to get thicker. It prevents FSH and LH.
29
What is ovulation?
At puberty eggs begin to mature and one is released every 28 days
30
What is Testosterone?
Main male reproductive hormone produced by the testes and it stimulates sperm production
31
What is follicle stimulating hormone (FSH)?
pituitary gland in the brain it causes egg to mature stimulates ovaries to release oestrogen
32
What is luteinsing hormone (LH)?
Produced in the ovaries. It is released on day 15 and causes eggs to be released.
33
What is progesterone?
secreted in the empty egg follicle in the ovary during ovulation
Helps maintain pregnancy and it stops production of FSH and LH. It maintains the lining of the uterus during 2nd half of the menstrual cycle so its ready to receive a developing embryo if egg is fertilised
34
What happens during menstrual cycle?
FSH: causes egg to mature stimulates ovaries to produce oestrogen
Oestrogen: build lining of uterus. inhibits FSH stimulates LH production
LH: causes release of mature egg from ovary
Progesterone: maintains uterus lining
35
What is a hormone?
A chemical messenger which controls body functions
36
How are hormones transported?
blood
37
How does the uterus change for pregnancy?
Lining thickens to prepare uterus for pregnancy. There is also an increases in blood vessels to make sure the baby is being supplied with the right amount of oxygen and vitamins.
38
What is contraception?
prevention of pregnancy. There are several categories of contraception hormonal and non hormonal methods
39
How does the contraceptive pill work?
- Use female hormones to prevent pregnancy
- contains low doses of oestrogen and progesterone
- hormones release FSH by the pituitary gland so no eggs mature
40
What are the cons of contraceptive pills?
- Raised blood pressure
- thrombosis
- Breast cancer
41
How does a condom work?
Thin latex sheath placed over the penis during intercourse to collect specimen.
Prevents egg and sperm meeting
42
What is a pro of a condom?
protection against STD's
43
What is a Con of condoms?
can get damaged and let sperm through
44
How does the IUD (Intrauterine devices) work?
- Small structures inserted into the uterus by a doctor
- Some contain copper and prevent any early embryos implanting in the lining of the uterus
- others contain progesterone to prevent build up of uterus lining
45
What is a pro of a IUD?
Very effective
46
What is a con of a IUD?
may cause period problem or infections
47
How does a diaphragm/cap work?
thin rubber diaphragm placed over the cervix before sex to prevent the entry of sperm
48
What is a Con of the diaphragm/cap?
If not placed correctly sperm may get past
49
How does an implant work?
Tiny tube inserted under your skin by a doctor and slowly releases progesterone
50
What is a pro of a implant?
99.5% effective
51
How does a patch work?
- Contains a mixture of oestrogen and progesterone
- stick patch to your skin replacing it every 7 days
- Hormones are absorbed directly into your blood stream
52
What is abstinence?
refraining from sexual activity
53
How does abstinence/rhythm method work?
- If people do not have sex they will not get pregnant
| - Abstaining from intercourse around ovulation or when an egg is in the oviduct means sperm cannot fertilise the egg
54
What is a con of Abstinence/rhythm method?
very unreliable
55
How does the surgical method for men work?
Sperm ducts are cut and tied prevents sperm getting into semen
56
What is the pro of the men surgical method?
permanent contraception
57
What is a con of a mans surgical method?
Needs a general anasthetic
58
How does the surgical method for women work?
oviducts are cut or tied to prevent the egg reaching the uterus and sperm reaching the egg
59
What is a pro of surgical method for women?
permanent contraception
60
What is a con of surgical method for women?
needs a general anaesthetic
61
What happens during In Vitro Ferilisation (IVF) treatment?
- IVF involves giving a mother FSH and LH to stimulate the maturation of several eggs
- The eggs are collected from the mother and fertilised by sperm from the father in the lab
- The fertilised eggs develop into embryos
- At the stage when they are tiny balls of cells, one or two embryos inserted into the mother's uterus
62
What is a way of using hormones to treat infertility?
Includes giving FSH and LH in a 'fertility drug' to a woman. She may then become pregnant in the normal way.
63
Even though fertility treatments gives a woman the chance to have a baby of her own what are some cons?
- very emotionally and physically stressful
- success rates are not high
- can lead to multiple births which are a risk to both the babies and the mother
64
Where is adrenaline produced and when is it released?
Produced by the adrenal gland in times of fear or stress. It increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for ‘flight or fight’.
65
Where is thyroxine produced and what does it stimulate?
Thyroxine from the thyroid gland stimulates the basal metabolic rate. It plays an important role in growth and development.
66
What is thryroxine levels controlled by?
negative feedback
67
What is a Gamete?
A sex cell
68
What is a chromosome?
long molecules of DNA are wound into these and stored in the nucleus
69
What is a Gene?
small section of DNA that determines/controls a characteristic
70
What is an allele?
An alternative version of a gene
71
What does dominant mean?
Type of allele that is always expressed, even if only one copy is present
72
What is recessive?
Type of allele that is only expressed if two copies are present
73
What is homozygous?
2 allele present are both the same
74
What is heterozygous?
2 alleles present are both different
75
What is genotype?
alleles present
76
What is phenotype?
characteristics expressed as a result of the alleles present
77
What is sexual reproduction?
joining of male and female gametes
e.g sperm and egg
pollen and egg cell
mixing of genetic information which leads to a variety in the offspring. involves meiosis
78
What is Asexual reproduction?
involves one parent and no fusion of gametes. no mixing of genetic information. This leads to genetically identical offspring only mitosis is involved
79
What type of cell is produced by meiosis?
gametes
80
What happens to chromosomes in gametes during meiosis?
the number of chromosomes halves and fertilisation restores the full number of chromosomes
81
What happens when a cell divides to form a gamete?
- Copies of the genetic information are made
- the cell divides twice to form four gametes, each with a single set of chromosomes
- all gametes are genetically different from each other
82
How does the new cells divide?
mitosis
83
What happens to the number of cells during mitosis?
increases
84
How many daughter cells are produced by meiosis?
4
85
Are the daughter cells from meiosis identical or different?
different
86
How many chromosomes does the daughter cells have compare to the parent cell?
23
87
Why is meiosis important?
ensures all organisms produced via sexual reproduction contain correct number of chromosomes
88
Why is mitosis important?
replaces cells that are old, lost or damaged
89
Are the daughter cells in mitosis identical or different?
identical
90
How many chromosomes does the daughter cells have compared to the parent cells in mitosis?
46
91
The genetic material in the nucleus of a cell is composed of what?
A chemical called DNA
92
What is DNA?
a polymer made up of two strands forming a double helix. Its contained in structures called chromosomes
93
What does each gene code for?
a particular sequence of amino acids, to make a specific protein
94
What characteristics are controlled by a single gene?
fur colour, eye colour
95
What is polydactyly caused by?
A dominant allele
96
What is Cystic fibrosis caused by?
A recessive allele
97
How many pairs of chromosomes does a normal human body cell contain?
23
98
How many pairs control characteristics only?
22
99
What are the sex chromosomes in females?
XX
100
What are the sex chromosomes in males?
XY
101
What is variation?
difference in the characteristics of individuals in a population
102
What causes variation?
- They genes they have inherited
- The conditions they have developed
- Combination of genes and the environment
103
What is mutation?
Change in the DNA
104
All species of living species have evolved from simple life forms from when?
3 billion years ago
105
How does evolution happen?
1. Variation exists in a species due to mutation
2. members of species with a certain phenotype are more likely to survive in a certain environment
3. Those who survive get together and mate to produce offspring
4. The parents who had the characteristic pass it down to offspring
106
What is selective breeding?
process by which humans breed plants and animals for particular genetic characteristics.
107
What does selective breeding involve?
choosing parents with the desired characteristics from a mixed population. They're bred together. From the offspring those with the desired characteristics are bred together. This continues over many generations until all the offspring show the desired characteristic.
108
What are some reasons for some chosen characteristics?
```
usefulness or appearance:
• Disease resistance in food crops.
• Animals which produce more meat or milk. ]
• Domestic dogs with a gentle nature.
• Large or unusual flowers.
```
109
What can selective breeding lead to and what does it mean?
‘inbreeding’ where some breeds are particularly prone to disease or inherited defects.
110
What is genetic engineering?
deliberate modification of an organisms genes
111
Why have plant crops been genetically engineered?
to be resistant to diseases or to produce bigger better fruits.
112
What are some modern uses of genetic engineering?
- Manufacturing insulin
- finding out where genes are expressed in the body
- producing crops which produce a greater yield
- producing crops that are resistant to disease
113
What is embryo transplantation?
separating groups of cells from a very young developing animal then putting the groups of cells into host mothers
114
What is a tissue culture?
growing group of cells from a plant on special jelly
115
How do they do genetic engineering?
1. extract DNA from a human cell. Use an enzyme to cut the insulin gene out of the DNA
2. Human cells contain a gene for making insulin
3. Use the same enzyme to cut bacteria DNA
plasmid
4. Bacteria cells contain a ring of portable DNA called a plasmid
5. Use a different enzyme to stick the human insulin gene into the bacteria plasmid
6. The plasmid holding the insulin gene is put into bacteria
7. The bacteria reproduce and start to make human insulin
116
What are some advantages for genetic engineering?
- genetic modification will reduce amount of insecticides used on crops
- GM can produce healthier versions of crops
- GM can lead to higher yielding crops which mean farmers can produce more from the same area of land
117
What are some disadvantages to Genetic engineering?
- Long term effects of GM crops on human health are not known
- Consumers wary of GM food
- Once established, GM crops would be almost impossible to remove from the environment
118
What are fossils?
remains of organisms which died thousands or millions of years ago
119
How do fossils forms?
- little oxygen present
- poisonous gas killed off decay causing organisms
- low temperature
120
What are some types of fossils?
- from hard parts of animals that don't decay easily
- from parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
- When parts of the organisms are replaced by minerals as they decay
- As preserved traces of organisms e.g footprints, burrows and rootlet traces
121
Why is the fossil record incomplete?
- Early forms of life were soft bodied
- Fossilisation requires very specific conditions
- Many fossils are destroyed by geological activity
- Many fossils have not been found yet
122
When does extinction occur?
when there are no remaining individuals of a species still alive
123
What does endangered mean?
very few members alive. They are in danger of becoming extinct imminently
124
What are some causes of extinction?
- Predators
- Global warming
- Changes to the environment
125
How can bacteria evolve rapidly?
reproduce at a fast rate
126
How can you reduce rate of development of antibiotic resistant strains?
* doctors should not prescribe antibiotics inappropriately, such as treating non-serious or viral infections
* patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains
* the agricultural use of antibiotics should be restricted.
127
How did antibiotic resistance come about?
through a process of natural selection
128
Why do we need to classify organisms?
- Classifying organisms according to their characteristics can help us study them and communicate clearly about them
- Can help us distinguish between different organisms that may look very similar
129
Who developed the 5 kingdom system?
Carl Linnaeus
130
What are the 5 kingdoms?
- Animals
- Plants
- Fungi
- Prokaryotes - single celled organisms without a nucleus
- Protists - eukaryotic single celled organisms
131
What 6 smaller groups can the kingdoms be split into?
- Phylum
- Class
- Order
- Family
- Genus
- Species
132
How are organisms made?
binomial systems of genus and species
133
Who created the 3 domain system?
Carl Woese
134
In the 3 domain system organisms are divided into what?
- Archaea
- Bacteria
- Eukaryota
135
What information did Carl Woese use to develop the 3 domain system?
Chemical analysis
| Studied prokaryotic cells
136
Why do scientists use evolutionary trees?
used to show how different species are related
137
How do scientists develop evolutionary trees?
study the fossil record for extinct species and current classification data for living organisms
138
What is a habitat?
An area where a population lives and finds the water, living space and other essentials it needs to survive
139
What is an abiotic effects?
effects of physical factors e.g light, temperature
140
What is a biotic effect?
Effect of other organisms of the same or different species e.g predators
141
What does population mean?
All the individuals of a particular species in a particular habitat at a particular time
142
What is a species?
a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding
143
What is a community?
formed of population of different species
144
What is an ecosystem?
a community of organisms that interact with each other and with the physical environment in which they are found
145
What is a food chain?
visual representation of one feeding relationships between organisms
146
What is a producer?
organism that makes its own energy using energy from the sun
147
What is a primary consumer?
organisms that consumes the producer
148
What is the trophic level?
position an organism occupies in a food chain
149
What is biomass?
mass of living material in an organism
150
What is a secondary consumer?
Organism that consumes the primary consumer
151
What is the tertiary consumer?
Organism that consumes the secondary consumer
152
What does the arrows in a food chain show?
flow of energy
153
Why doe the amount of biomass decrease along a food chain?
resperation
movement
maintaining body temperature
waste
154
What is deforestation?
Process where natural forests are removed
155
What are the consequences of deforestation?
reduce biodiversity
too much CO2
animals becoming extinxt
increase in floods
156
What are some advantages of deforestation?
More jobs created when factories are built
farms provide us with food
people able to travel easily
157
How are animals adapted for cold environments?
thick coat for warmth
| greasy hair to allow water to run down it
158
What are some abiotic factors which can affects the community?
light intensityy
temperature
moisture levels
159
What are some biotic factors which can affect the community?
availability of food
new predators
new pathogens
160
What does the carbon cycle do?
returns carbon from organisms to the atmosphere as carbon dioxide to be used by plants in photosynthesis
161
What does the water cycle do
provides fresh water for plants and animals on land before draining into the seas. Water is continuously evaporated and precipitated.
162
When can pollution occur?
in water, fertiliser
in air, smoke and acidic gases
on land, landfill
163
What is contributing to global warming?
levels of carbon dioxide and methane in the atmosphere rising
164
Scientists and concerned citizens have put in place programmes to reduce the negative effects of humans on ecosystems and biodiversity what are some examples?
* breeding programmes for endangered species
* protection and regeneration of rare habitats
* reintroduction of field margins and hedgerows in agricultural areas where farmers grow only one type of crop
* reduction of deforestation and carbon dioxide emissions by some governments
* recycling resources rather than dumping waste in landfill
165
How much biomass from each trophic level is transferred to the level above?
%
