3-6 Markers Flashcards by Simone Laird

Explain how an impulse is transmitted from one neurone to another (4)

Synapse
• Synapse is a gap between two neurones
• Neurotransmitters
• Diffuse across the synapse
• Electric impulse transmitted down next neurone

How well did you know this?

Not at all

Perfectly

You see a car and need to jump out of the way.
Describe how the reflex arc keeps you safe from danger (6)

• Stimulus is the light reflecting from car
• Receptor in eve detect light
• Electrical impulse transmitted through sensory neurone
• Neurotransmitters cross synapse - a gap between two neurones
• Relay neurone
• Motor neurone
• Effector is muscle
• Response is muscles contract - jump from road
• Bypasses brain to speed up reactions

How well did you know this?

Not at all

Perfectly

Explain how convex and concave lenses can be used to correct vision (6)

Concave / diverging lens:
• Corrects short-sightedness
• Lens bends light away from concave lens onto the cornea
• lens then refracts light and focuses light onto retina

Convex / converging lens:
• Corrects long-sightedness
• Lens bends light from the convex lens onto the cornea
• lens then refracts light and focuses light onto retina

How well did you know this?

Not at all

Perfectly

Describe how hormones control blood glucose levels (6)

Lowering blood glucose levels:
• Pancreas secretes insulin
• Converts glucose to glycogen
• Increases glucose absorption into cells and increases rate of respiration
• Glycogen stored in liver
Increasing blood glucose levels:
• Pancreas secretes glucagon
• Glucagon converts glycogen in liver to glucose

How well did you know this?

Not at all

Perfectly

Explain how type-1 and type-2 diabetics control their diabetes (6)

Type-1 diabetics: Produce no insulin
• Insulin injections to lower glucose blood concentration
• Insulin converts glucose to glycogen (stored in liver)
• Exercise increases rate of respiration - lowers glucose conc.
• Low sugar diet prevents high blood glucose concentration
Type-2 diabetics: Produce insulin
• Exercise
• Low sugar diet

How well did you know this?

Not at all

Perfectly

Explain how adrenaline effects organs for flight or fight (6)

Heart:
• Increases heart muscle contractions & higher blood pressure
• Increased oxygen & glucose to cells
• Increased respiration & more energy released
Liver:
• Converts glycogen to glucose
• Increases glucose levels in blood
Blood vessels:
• Widen blood vessels to muscles
• Narrows blood vessels to non-vital organs
• Increases blood supply to muscles

How well did you know this?

Not at all

Perfectly

Explain how negative feedback controls thyroxine levels in the blood (6)

Low thyroxine levels in the bloodstream:
• Stimulate the hypothalamus to release TRH
• This causes the pituitary to release TSH
• Causing the thyroid releases more thyroxine
(H) Effects of Thyroxine
Normal thyroxine levels in the bloodstream:
• Inhibit TRH release from the hypothalamus
• Inhibiting the release of TSH from the pituitary
• Thyroid releases less thyroxine

How well did you know this?

Not at all

Perfectly

Explain how ADH regulates water reabsorption in the collecting duct (6)

• Hypothalamus detects blood water levels
• Pituitary gland secretes ADH
When water levels are low / dehydrated:
• ADH levels increase
• Permeability of collecting duct membrane increases
• More reabsorption of water • Decreased volume of urine
When water levels are high / hydrated:
• ADH levels decreases
• Permeability of collecting duct membrane decreases
• Less reabsorotion of water
• Increased volume of urine

How well did you know this?

Not at all

Perfectly

Explain how vasodilation and vasoconstriction help control body temperature (6)

Vasoconstriction:
• Blood vessel to capillaries near skin to narrow
• Restricts blood flow to surface of skin
• Reduces heat loss to surroundings
• Increases bod temperature
(S) Vasoconstriction & Vasodilation
Vasodilation:
• Blood vessel to capillaries near skin widen
• Increases blood flow to skin
• Increases heat loss to surroundings
• Decreases bod temperature

How well did you know this?

Not at all

Perfectly

Explain how hormones control the menstrual cycle (6)

• FSH released by pituitary gland causes egg follicle to grow and mature
•Oestrogen released from ovary
• Oestrogen causes uterus lining to thicken
• Oestrogen inhibits FSH / causes LH to be released
• LH spike on day 14
• LH causes ovulation / egg to be released from ovary
• Progesterone maintains uterus lining
• If fertilisation progesterone levels stay high to maintain uterus lining
• If no fertilisation progesterone levels decrease
• Uterus lining breaks down - menstruation

How well did you know this?

Not at all

Perfectly

Explain how the hormones in the contraceptive pill prevent pregnancy (4)

• Oestrogen and progesterone in combined pill
• Oestrogen inhibits FSH production
• Egg follicle doesn’t grow and mature
• No LH spike
• No ovulation / egg not released
Contraceptive Pill
• Progesterone causes mucus around cervix
• Reducing sperm ability to enter uterus
• Less sperm and no egg means no fertilisation

How well did you know this?

Not at all

Perfectly

Explain which two hormones help the woman produce and release mature eggs (4)

FSH - causes multiple egg (follicles) to grow and mature
• LH - causes ovulation / egg release

How well did you know this?

Not at all

Perfectly

Describe how the mature eggs are used in IVF treatment so that the woman may become pregnant (4)

Multiple eggs removed from ovary
• Male provides sperm sample
• Sperm and eggs are mixed
• Egg is fertilised by sperm
• Embryos incubated
• Multiple embryos placed into uterus of mother

How well did you know this?

Not at all

Perfectly

Describe how pre-implantation genetic diagnosis (PGD is used to screen embryos for genetic disease (4)

PGD screens embryo for genetic diseases
• during IVF
• Cell removed from fertilised embryos
• Cell’s DNA screened
• If faulty gene is found - embryo destroyed & not used

How well did you know this?

Not at all

Perfectly

Describe how pre-implantation genetic diagnosis (PGD is used to screen embryos for genetic disease (4)

• PGD screens embryo for genetic diseases
• during IVF
• Cell removed from fertilised embryos
• Cell’s DNA screened
• If faulty gene is found - embryo destroyed & not used

How well did you know this?

Not at all

Perfectly

Describe how Chorionic villus sampling
(CVS) is used to screen a foetus for genetic disease (4)

• CVS screens foetus at 10-13 weeks
• Cells of chorionic villus (in placenta)
• Is genetically identical as foetus
• Analyse genome of cells from chorionic villus
• If faulty gene found - indicates genetic disorder

Describe how amniocentesis is used to screen a foetus for genetic disorders (4)

• Amniocentesis done between 15-16 weeks
• Needle inserted into amniotic fluid and extracted
• Amniotic fluid contains cells from foetus
• Analyse genome of cells from amniotic fluid for genetic disorder.

Describe the uses of gibberellins, ethene & auxin in plants (6)

Auxins:
• Selective weedkiller
• Targets broader leaved plants
• Causes uncontrollable growth / kills them
• Rooting powder and stimulates root growth
Gibberellins:
• Used to make seeds germinate when the farmer wants them to
• Overcome photoperiodism
• Make plants flower
• Helps produce larger fruits
Ethene:
• Used to ripen fruit

Explain how auxins control how a plants grows towards light and control the roots downwards growth (6)

Phototropism:
• Auxins move to shaded region of shoot
• Auxins stimulate cell elongation
• Shoot grows and bends to light
Gravitropism:
• Auxins in roots fall to bottom/base of root due to gravity
• Auxins in root inhibit/stop cell elongation at bottom of root
• Cell elongation is faster at top of the root
• Root grows and bends downwards

Describe how water is cycled in the environment (6)

• Energy from sun transferred to sea/ocean/lakes
• Water in seas/oceans/lakes evaporates
• Condenses into liauid (in clouds)
• Water falls as precipitation into seas/ocean/lake
• Water absorbed by by plants for photosynthesis
• Water moves through and out of plant by transpiration
• Animals drink water
• Animals urinate/sweat/breath/excrete water back into atmosphere

Describe how Carbon is cycled in the environment (6)

• Carbon dioxide absorbed by plants from atmosphere for photosynthesis
• Photosynthesis converts carbon dioxide to glucose
• Glucose stored as starch
• Animals eat plants and digest starch to glucose
• Glucose used by animals for respiration
• Carbon dioxide is breathed out into atmosphere by animal
• Organism dies and fungi /bacteria decompose dead organism
• Detritus feeders/fungi/bacteria use glucose for respiration
• Release carbon dioxide into atmosphere
• Dead organisms formed fossil fuels
• When fossil fuels combusted carbon dioxide released into atmosphere

Explain how polar bears and camels are adapted to survive in extreme conditions (6)

Polar bears:
• White fur - as camouflage from prey on snow • Thick layers of fat and fur - for insulation • Small surface area to volume ratio to minimise heat loss • Greasy coat to help reduce heat loss • Large feet to distribute their load and increase grip on the ice • Small ears decrease surface area to volume ratio to reduce heat loss
Camels:
• Large, flat feet to spread weight on the sand • Thin fur to allow easy heat loss • Large surface area to volume ratio to maximise heat loss • Fat store in hump
Provides them with energy • Lose very little water via urination & sweating • Slit-like nostrils and two rows of evelashes to help keep out sand • Long ears increase surface area to volume ratio to increase heat loss

Compare asexual and sexual reproduction (6)

Sexual reproduction pros:
• Genetic variation increases chances of adapting / surviving changing environments
• Selective breeding to breed for characteristics

Sexual reproduction cons:
• Organisms need to find a mate to breed • Requires more energy than asexual reproduction
• Slower than asexual reproduction 2

Asexual reproduction pros:
• Only one parent required
• Requires less energy than sexual reproduction
• Faster than sexual reproduction
• Many offspring produced quickly

Asexual reproduction cons:
• No genetic variation between offspring
• Therefore, difficult for offspring to survive environment changes

Describe the structure of DNA (4)

• Double helix
• Two strands of DNA wrapped around each other
(S) Structure of DNA
• Backbone made from phosphate and sugar
• Bases are A (adenine), T (thymine), G (guanine), C (cytosine)
• A complementary base pairs with T
• G complementary bas pairs with C
• Nucleotide formed from a sugar, base and phosphate
• (Weak) hydrogen bonds formed between bases

Compare haploid & diploid cells in humans (4)

Diploid cells • Body cells • Two sets of chromosomes • Two sets of 23 chromosomes • Produced by mitosis Haploid cells • Gametes / sex cells / sperm & egg cells • One set of chromosomes One set of 23 chromosomes • Produced by meiosis

Describe how gametes are formed by meiosis (6)

1• Chromosomes make identical copies of themselves 2• Similar chromosomes pair up 3• Sections of DNA get swapped between chromosomes 4• Pairs of chromosomes divide 5• The chromosomes divide again Meiosis • Two cell divisions Forming: • Four cells • Haploid • Non-Identical • Gametes / sex cells / sperm & egg cells

Compare mitosis and meiosis (6)

Mitosis: • One cell division • Forms Two • Geneticallv Identical • Diploid / two sets of chromosomes • Body cells Meiosis: • Two cell divisions • Forms four • Geneticallv non-identical / different • Haploid / one set of chromosomes • Sex cells / gametes / sperm & egg cells

Describe how sex is inherited and state the probability that a child will be female (6)

• Male genotype is XY • Female genotype is XX • Female can only pass on X sex chromosome • If male passes on X chromosome • Child is XX and female • If male passes on Y chromosome • Child is a XY and male • 50% chance of a female child

Explain how two parents with brown eyes can have a child with blue eyes (6)

• Mother is Bb • Father is Bb • Both parents are carriers of blue eve allele • Mother passes on recessive b allele • Father passes on recessive b allele • Child has two recessive b alleles • 25% chance of bb

Explain how two parents without cystic fibrosis can have a child with cystic fibrosis (6)

• Mother is Ff • Father is Ff • Both parents are carriers of cystic fibrosis allele • Mother passes on recessive fallele • Father passes on recessive fallele • Child has two recessive falleles • 25% chance of ff

Mendel crossed pea plants that produced round seed with pea plants that produced wrinkled seeds. All the offspring produced round seeds. He then crossed these offspring with each other. Some pea plants in the next generation produced round seeds and the others produced wrinkled seeds Explain how this showed that some inherited traits are not expressed in an organism (4)

• The first generation were heterozygous • To have wrinkled seeds: • Offspring need two wrinkled alleles/are homozvgous • 25% offspring have wrinkled seeds • Wrinkled is recessive / round is dominant

Heavy snowfall in the Arctic Circle covered the ground leading to a selection pressure on the snow hares. Some hares are white, and some hares are brown. Explain which hare would most likely survive (4)

• Variation: White and brown hares • Environment change/selection pressure: white snow • White hares can camouflage, brown hares can't • White hares survive and breed • Pass their beneficial alleles/variation onto offspring • Natural selection

Antibiotics can be used to treat infections & some are resistant to antibiotics. With reference to Darwin's Theory of Natural Selection, explain which bacteria would most likely survive if the course of antibiotics is not completed (4)

• Variation: some bacteria have high resistance, medium resistance and low resistance • Environment change/selection pressure: antibiotics • If antibiotic course not finished high resistant bacteria survive • High resistant bacteria divide and pass on beneficial alleles/genes to offspring.

Describe how speciation can lead a new species of bird evolving from the original species (4)

• bird separated / isolated • Genetic variation / mutation (in bird population) • Birds with alleles/genes best suited to their environment survive • Beneficial alleles / genes passed onto offspring • After a long time / many generations populations can no longer breed

Lamarck's theory is different from Darwin's theory. Use Lamarck's theory to explain how an elephant's trunk became longer over time.

• Elephant stretched its trunk to reach food • Stretched trunk passed onto offspring (S) Lamarck Do not accept reference to genes

A farmer wants to breed fast horses. Describe how the farmer would do this (4)

• Select desired characteristic in horses (fast horses) • Breed fast horses • Pass their beneficial alleles/variation onto offspring • Select desired characteristic in offspring • Breed offspring with desired characteristic • Repeat the process

Compare the advantages and disadvantages of selective breeding (6)

Advantages of Selective Breeding: • Organisms grow faster • Organisms cope better with environmental conditions • Increase in yield • New varieties may be economically important • Producing more or better-quality food .Animals can be selected that cannot cause harm, for example cattle without horns Disadvantages of Selective Breeding: • Reduces gene pool. Only certain alleles are selected Others become rare or disappear. So, alleles that might be useful in the future are no longer available • All the organisms are very similar and so if a change in conditions (e.g. a new disease) affects one organism, all the others are affected • Can create physical problems in specific organisms, e.g. large dogs can have faulty hips due to not being formed correctly

Compare the advantages and disadvantages of genetic engineering (6)

Advantages: • faster and more efficient • Improve crop yields or crop quality. • Introduce herbicide resistance, less herbicides being used • Insect and pest resistance Disadvantages: • Transfer of the selected gene into other species. benefits one plant may harm another • GM crop seeds are often more expensive • GM crops could be harmful

Describe how adult cell cloning is used to produce a cloned sheep (6)

• Adult cell/skin cell removed from one sheep • Egg cell removed from another (female) sheep • Remove nucleus from egg cell • Take nucleus from adult (skin) cell • Put nucleus from adult (skin) cell into empty egg • Give cell a (mild) electric shock • Causes egg cell to divide / form embryo • Place (embryo) into womb/uterus of (surrogate) sheep