Reproduction
Hormones are secreted by glands or made artificially by drug companies.
(a)
(i) Name the gland that secretes testosterone.
Testes
Define the term gene
(length of) DNA / part of chromosome / on a chromosome,
that codes for a protein or polypeptide or enzyme / controls a characteristic;
Fig. 1.1 shows several villi from the ileum, which is part of the small intestine.
(a) State the name of one other part of the small intestine.
duodenum
State one substance, other than sucrose, that is produced in leaves and translocated to other parts of the plant.
amino acids ;
R proteins
(b) (i) Describe what happens at ovulation.
release of an, egg/ovum/oocyte ;
either
from, follicle / ovary ;
or
into, oviduct/ fallopian tube ;
a) The production of human gametes involves the type of nuclear division known as meiosis.
State two reasons why meiosis is suitable for gamete production.
1
2
halves the number of chromosomes / diploid to haploid;
ignore halves the genetic material
produces variation / AW;
Lipase is involved in the breakdown of fats.
State the two products of fat digestion.
fatty acids
glycerol
(b) (i) Describe the function of stomata.
movement of gas/oxygen/carbon dioxide, into and out of leaf; for, photosynthesis/ respiration;
allows transpiration ;
enables water to be pulled up the plant/AW;
(i)
Fig. 5.2
State three ways in which a sperm cell differs from an egg cell.
1
2
3
flagellum/tail/streamlined;
motile/swim /AW;
smaller/ reference to actual sizes ;
acrosome/enzymes in packet on head ;
no food store;
less cytoplasm;
contains X or Y (chromosome) ;
Plants that live in hot, dry environments show adaptations for survival.
State three structural adaptations of these plants.
1.
2
3.
leaves, small / reduced to spines / are needles; A small surface area no leaves;
curled / rolled, leaves;
hairs on the, leaves / stems ;
thick (waxy) cuticle; R 'skin' / waxy cuticle unqualified sunken stomata / AW ;
few stomata;
fleshy / succulent, leaves / stems; A described as reserves / stores of water small surface area: volume ratio;
deep roots ;
long / extensive, shallow roots; A long roots near the surface
Physical digestion by teeth breaks down food into smaller pieces. Explain the importance of food being physically broken down into smaller pieces.
any three from:
to increase surface area ; for chemical digestion;
by (named) enzymes ;
Responses to light are coordinated by plant growth substances known as auxins.
Explain the role of auxins in coordinating the response.
auxins stimulate cell elongation ;
cells have turgor pressure causes cells to lengthen ; more auxins on shaded side:
more, lengthening / growth, on shaded side causes bending :
(c) Marsupials differ from other mammals by giving birth to relatively undeveloped offspring.
Female humans have a placenta and therefore give birth to more developed offspring.
(i) Describe the role of the placenta in humans.
gas exchange / named example with direction ; transfer of (dissolved) nutrients, from maternal (circulation) / to fetal;
transfer of excretory products, from fetal / to maternal ; by diffusion;
produces / secretes, (named) hormone ;
passive immunity / antibodies, from maternal/to fetal ; prevents/limits, mixing of blood; ref to regulating blood pressure;
AVP; e.g. maternal/fetal attachment point e.g. ref to counter current flow / maintains
concentration gradient
e.g. hormone function describe
Describe the process of protein synthesis in a cell in your answer include the roles of DNA, MRNA, and ribosomes.
Scientists used enzymes and bile in the early development of biological washing powders.
Outline the roles of bile in the body.
any four from: emulsification ;
increased surface area of fat (globules) ; faster, digestion / breakdown (of fat) ; by lipase / to fatty acids and glycerol ; neutralises, (stomach) acid / chyme / gastric juice ; alters / increases, pH for (pancreatic / intestinal) enzymes
/AW ;
denatures, pepsin / stomach, enzymes
Define the term transpiration.
evaporation of water, from (surfaces of) mesophyll; movement / diffusion / loss of, water vapour : from, leaves; A (named) aerial / upper, parts;
through / from, stomata / cuticle ;
Explain the advantages of sexual reproduction to an animal species.
maintain/ increase, population ;
allows variation ;
(variation) caused by meiosis ;
for example through crossing over/independent assortment;
random fusion of gametes;
ability to express recessive traits/AW;
adaptation to newl changed environments ;
(allows) natural selection /evolution / formation of new species ;
Scientists think that plants of L. polyphyllum growing at high altitudes may evolve into a new species.
Explain how natural selection could lead to the evolution of a new species of lily.
different environments have different selection / competition pressures;
variation occurs (at fertilization / meiosis;
ref to mutation ;
best adapted organisms most likely to survive; (those that survive) pass on their alleles / genes;
competition for survival;
cross pollination ensures more variation (than self-pollination) ;
reproductive isolation (by different flowering times) ; changes enhanced over generations;
no cross-pollination between low and high altitude plants;
Describe and explain how the structure of a villus is adapted for its function.
Finger-like projections / microvilli → increase surface area for faster absorption
Single layer of epithelial cells → short diffusion pathway
Dense capillary network → maintains steep concentration gradient; thin walls reduce diffusion distance
Lacteal → absorbs fats/chylomicrons too large for capillaries
Epithelial cells rich in mitochondria → ATP for active transport of nutrients
Water moves into plants from the soil and exits through the leaves.
(a) Explain how water moves from the soil into the root.
root hairs;
water moves, from high water potential to low water potential / down water potential gradient;
by osmosis:
through partially permeable membrane ; through protein pores (in membrane):