Reproduction Flashcards
Sexual reproduction (definition, advantages and disadvantages)
Involves the joining of two gametes by meiosis from two parents to produce non-identical offspring, inheriting characteristics from both parents
Advantages:
-increase variation
-organisms can adapt to new environments
-disease is likely to affect population (due to variation)
Disadvantages:
-takes long time and energy to find mates
-not possible for isolate members
Asexual reproduction(definition, advantages and disadvantages)
Involves only one parent that produces offsprings that are genetically identical to their parents by mitosis
Advantages
-population can increase rapidly
-can exploit suitable environments quickly
Disadvantages
-decreases variation
-vulnerable to change in conditions (can only exploit suitable environments)
-disease is more likely to affect whole population
Fertilization
Fusion of male and female gamete to produce a zygote that undergoes cell division (mitosis) and develops into an embryo.
Explanation:
-an egg cell and sperm cell are haploid cells, containing 23 chromosomes each
-when fertilization occurs, the fertilized egg cell will form a zygote, a diploid cell with 46 chromosomes
-the zygote will contain a mixture of genetic info from both parents so will result in genetic variation
Structure of insect pollinated flower
-Sepals:protects unopened flower
-Stamens:male part of the flower consisting of filament and anther
-Filament:positions anther to release male sex cell (pollen grain)
-Anthers:produces and releases the male sex cell
-Pistils:female part of the flower, consisting of ovule, ovary and stigma
-Stigma: top of the female part of the flower which collects pollen grains
-Ovary:produces the female sex cell(ovum)
Adaptations for insect-pollinated
-Petals: large and brightly colored
-Scent and nectar: scented nectar
-Number of pollen grains: moderate-insects transfer pollen grains efficiently (high chances of pollination)
-Pollen grains: sticky and spiky to hang onto insects
-Anthers: inside flower, stiff and firmly attached to brush against insects
Stigma:inside flower, sticky so pollen grains stick to it when an insect brushes past
Adaptations of wind pollinated flower
Petals:small and dull (green or brown)
Scent and nectar:no scented nectar
Number of pollen grains:large amounts-most pollen grains are not transferred to another flower(increase chances of pollination)
Pollen grains:smooth and light so can easily be carried by wind
Anthers:outside flower, loose on long filaments to release pollen grains easily
Stigma:outside flower, feathery to catch drifting pollen grains
Growth of the pollen tube followed by fertilization
- pollen grain will land on stigma
- pollen tube grows out of the pollen grain and down the style into the ovary into the ovule
- the male nucleus travels down this tube from the pollen grain and fuses with the female egg nucleus in the ovule to form a zygote, zygote will undergone mitosis to develop to form a seed
- ovule will become the seed, ovule wall the fruit coat and ovary the fruit
Conditions needed for seed germination
Water: allows the seed to swell with water and activates enzymes to break down the food reserves in seeds(starch)
Oxygen:for aerobic respiration to release energy for growth of seed
Warmth:optimum temp for enzymes to increase growth rate and enzyme activity
Germinating seeds structure and utilization of food reserves in seeds
-Embryo:young root (radicle) and shoot (plumule) that will become the adult plant
-Food store:for aerobic respiration to release energy for growth of seed
-Seed coat:optimum temp for enzymes to increase growth rate and enzyme activity
Utilisation of food reserves in seeds
-cotyledon contains starch which is used as a food store in seeds
-amylase will break down starch into glucose
-glucose will be used in aerobic respiration to release energy for growth
-this will continue until the seed germinates and can photosynthesize independently
Runners and cuttings (reproduce asexually)
Runners (natural method) : some plants grow side branches that contain plantlets which specialize into forming root hair cells when they touch the ground.
These plantlets will grow roots allowing asexual reproduction.
Cuttings(artificial): tissue sample is scrapped from parent plant. Tissue samples are placed in agar growth medium containing nutrients and auxins. Samples develop into tiny plantlets. Plantlets are planted into compost
Male reproductive system
Sex gland: produces fluid called semen that will provide the sperm cell with nutrients
Sperm duct:sperm passes through the sperm duct to be mixed with fluids produced by the sex gland
Urethra:tube inside the penis that can carry out urine or semen, a ring of muscle in the urethra prevents the urine and semen from mixing
Testis: contained in a bag of skin (scrotum) and produces sperm (male gamete) and testosterone (hormone)
Penis: passes urine out of the body from the bladder and allows semen to pass into the vagina of a woman during sexual intercourse
Female reproductive system
Oviduct: connects the ovary to the uterus and is lined with ciliated cells to push the released ovum towards the uterus for fertilization
Ovary: contains ova(female gametes) which will mature and develop when FSH is released
Uterus:muscular bag with a soft lining where the fertilized egg fell will be implanted to develop into a fetus
Cervix:ring of muscle at the lower end of the uterus to keep the developing fetus in place during pregnancy
Urethra:tube that passes urine out of the body from the bladder
Vagina:muscular tube that leads to the inside of the woman’s body, where the males penis will enter during sexual intercourse
Hormones and menstrual cycle
Menstrual cycle: recurring process in which the uterus lining is prepared for pregnancy, and if pregnancy does not occur, the lining will shed at menstruation
Process:
1.FSH
-the pituitary gland will secrete FSH and will cause an egg to mature and develop in the ovary
-stimulates ovaries to release oestrogen
2.Oestrogen
-oestrogen is secreted in the ovaries and will stop FSH being produced (so only one egg matures in a cycle)
-stimulates pituitary gland to release the hormone LH
3.LH
-LH will cause the mature egg to be released from the ovary
-stimulates ovaries to release the hormone progesterone
4.Progesterone
-stimulates the growth of blood vessels in the uterus lining for pregnancy
-if fertilized egg cell is implanted into the uterus lining, progesterone will maintain pregnancy by keeping uterus lining thick and rich in blood vessels to cushion the fertilized egg
Role of placenta
- As the embryo develops, the placenta forms
- the developing fetus is connected to the placenta by the umbilical cord
- this allows the diffusion of glucose (food) and oxygen from the mother’s blood to the developing fetus for growth
- also carries amino acids to build protein for growth and repair of the developing fetus
- waste carbon dioxide and urea will be taken away from the developing fetus to be passed into the mothers blood and secretes the hormone progesterone which maintains the pregnancy (uterus lining)
Amniotic fluid
The uterus is surrounded by the amniotic fluid in the amniotic membrains, this cushions and protects the fetus from knocks and bumps as it develops
Roles of oestrogen and progesterone
Oestrogen -breasts develop in preparation for breastfeeding -hips grow in preparation for childbirth -the menstrual cycle begins -hair grows(pubic regions, armpits) -acne may form Progesterone -voice breaks -sperm production begins -muscles and penis grows -hair grows(pubic regions, face, armpits, chest) -acne may form
