Transcript Reproduction_animal_HKDSE_common misconception

Common misconceptions in
Biology
Reproduction and development
Misconception:
Sexual reproduction involves two
parents while asexual
reproduction involves one parent.
• some flowering plants may occasionally
carry out self-fertilisation
• Tapeworm
Misconception:
• Offspring produced from self-fertilisation
have no genetic variation, similar to those
produced from asexual reproduction.
Wheat is largely self pollinating.
• In fact, self fertilisation is a sexual
process because it involves meiosis in
the formation of gametes and fusion of
gametes.
• However, unlike cross-fertilisation, selffertilisation involves only one parent.
Therefore the genetic variation of the
offspring is less than that from cross
fertilisation in which genes from two
different parents are combined.
Misconception:
• One of the advantage of using seeds
over using corms in plant reproduction
is that genetic variation results from
seeds will always give rise to better
adaptation to the environment.
• Genetic variation
may give rise to
new varieties which
MAY or MAYNOT be
better adapted to the
environment
Misconception:
• Pollen grains are the male gametes of
flowering plants.
• Pollen grain
should be treated
as a carrier of
the male
gametes
Misconception:
• pollen grains, such as being light and
produced in large numbers, are important
for the dispersal of the offspring
• mistaken the pollen grains as equivalent
to the seeds or spores.
• pollen grains -- as an adaptation of
flowering plants (and gymnosperms)
for reproduction on land.
• The use of agents to increase chance of
cross pollination
Bee with pollen grains packed
on its legs
Misconception:
• The growth of a seedling can be measured
by the change in dry mass.
• The dry mass of a seedling is made up of
cytoplasm of new cells and stored food in
the seed, which decreases in mass with
the growth of the seedling.
• During seed germination before the
development of green foliage leaves, the
seedling uses up stored organic food
for respiration and for the formation of
new tissues. In this case, growth occurs
rapidly due to formation of new cells.
Misconception:
• Each maize grain is a seed produced from
sexual reproduction.
Maize grain is a one-seeded fruit is that it
normally has two layers of wall covering
the seed. The outer layer is the fruit wall
or pericarp while the liner layer is the seed
coat or testa.
Misconception:
• The edible receptacle of the apple
provides the food for seed germination
• The flesh of the fruit is an adaptation for
attracting animal for animal dispersal
• The stored food for seed germination is
provided by the seeds themselves
Misconception:
• During a menstrual cycle, ovulation
occurs when the uterine lining is
thickest.
• The time for ovulation could be
approximately estimated as 14 days
backward from day 24 —the day where
menstrual flow starts, that means the
beginning of the next cycle.
Misconception:
• If the oviducts of a woman are tied up and
cut, she will not have ovulation and
menstruation
• The secretion of hormones into the blood
is not affected by ligating the oviduct.
• This means that ovulation and the
menstrual cycle, being under the control
of pituitary hormones and ovarian
hormones respectively, still occur
normally after the operation.