Lecture notes
Reproduction notes iGCSE biology
Notes for reproduction from iGCSE and GCSE biology. Very in depth and allowed me to achieve a grade 9
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What are the differences between asexual and sexual reproduction? Asexual:One parent
Genetically identical offspring
Sexual:
Two parents
Genetically varied offspring
What are advantages of asexual reproduction? Population rapidly increases when
the conditions are favourable. Time and energy efficient method of reproducing.
Reproduction completed much faster than sexual reproduction
What are disadvantages of asexual reproduction? Limited genetic variation.
Population only suited to one habitat. Disease likely to affect whole population
What are advantages of sexual reproduction? Increases genetic variation. Can
adapt to new environment. Disease is less likely to affect population
What are disadvantages of sexual reproduction? Time and energy to find mates.
Difficult for isolated members to reproduce. Longer gestation period
What are the stages of sexual reproduction? 1. Gametes are produced
2. The male gamete is transferred to the female gamete
3. Fertilisation occurs
4. The zygote develops into a new organism
What is asexual reproduction via budding? Cells from the parent divide via mitosis
to form a structure that breaks away from the parent body and grow into a new
organism. OCCURS IN HYDRA
What is asexual reproduction via runners? Stem grown outwards horizontally away
from the parent plant. The runners will drop down to hit the soil, and will begin
to form its own roots and leaves. The runners will then detach - forming a clone.
Uses mitosis so all cells are identical. These runners are specialised and can be
cut and planted separately to form an identical plant. OCCURS IN STRAWBERRY
What is asexual reproduction via tubers? Tubers form at the end of branches from
the same stem. Each plant can produce several new plants which are called buds.
OCCURS IN POTATO
What is asexual reproduction via bulbs? The function of the bulb is to store food
for the plant. There will be the main flower bud, and a lateral bud. A new plant
will then begin to grow from the lateral bud, creating a genetically varied plant.
OCCURS IN ONION
What is asexual reproduction in taking cuttings? Take off a side shoot from
the plant and plant the side shoot in compost. Place this in a warm environment to
speed up growth and a genetically identical plant will grow. OCCURS IN STRAWBERRY
What is asexual reproduction in micro-propagation? Stems and explants are
removed from the plant. They are then sterilised kill microorganisms. They are
placed in an agar medium containing nutrients and plant hormones to encourage
growth. The explants with shoots are then transferred to another medium with a
different balance of plant hormones to cause root formation. Once the explants have
grown roots, they are transferred to greenhouses and placed in compost. The plants
then gradually acclimatise to normal growing conditions. The greenhouse is kepy
very moist to reduce water loss in young plants. OCCURS IN BANANA
What is pollination? The process which pollen is transferred from the anther to
the stigma
What are both types of pollination? Wind pollination and plant pollination
Insect pollinated plant
Wind pollinated plant
What is the function of a petal? To attract insects
What is the function of the sepal? Protects the flower while in bud
What is the function of the petiole (stalk)? Supports the flower to make it
easily seen by insects, and to be able to withstand wind
What is the function of the nectary? Produces nectar to attract insects
What is the function of the stamen? The male reproductive part of the flower, made
up of anther and filament
What is the function of the anther? Contains pollen sacs, in which pollen grains
are formed. Pollen contains male sex cells
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