Reproduction Flashcards
Sexual Reproduction
Any multicellular organism that involves the fusion of two gametes (from each parent) to form a zygote
Diploid
Full set of genetic information in an organism (46 for humans)
Haploid
Half a set of genetic information in an organism (23 for humans)
Advantages of sexual reproduction
- All offspring are different (variation)
- Species can adapt to the new environment
- A disease is less likely to effect the individual’s in a population
Disadvantages of sexual reproduction
- Need to find a mate (requires time and energy so few offspring are produced)
- Needs two people
Zygote
A diploid cell resulting from the fusion of two haploid gametes. A fertilised ovum
Mitosis
Produces diploid ‘daughter’ cells that are genetically identical to their parents
Advantages of asexual reproduction
- Only one parent is needed
- Faster than sexual reproduction
- Population can increase rapidly
- Requires less energy
Disadvantages of asexual reproduction
- It does not lead to variation in the population
- The species may be only suitable for one habitat
- Disease effects all individuals in the population
Meiosis
- Sexual reproduction, a form of cell division in the formation of gametes
- Genetically different
- 2 parents
- Produces 4 cells (chromosome number is halved)
- 2 divisions
What does meiosis produce?
-Produces haploid non-identical sex cells called gametes. These fuse to form a diploid fertilised egg.
- In animals it produces sperm and egg cells
- In plants it produces pollen and egg cells
Mitosis
- Asexual reproduction
- Genetically identical
- 1 parent
- Produces 2 cells
- 1 division
What is mitosis used for?
Growth, Repair, Replace
What are gametes)
- Sex cells such as egg or sperm cells
- They are haploid (half genetic information)
Where does Meiosis occur?
Occurs in reproductive organs
Where does mitosis occur?
-Everywhere in the body
What must occur prior to meiosis?
Interphase
First stage of meiosis
- Chromosomes line up along the equator
- Pairs of chromosomes are separated and move to opposite poles of cell (random for variation)
- Chromosome number is halved
Second stage of meiosis
- Chromosomes line up along equator
- Chromosomes separate randomly to opposite poles
- Four unique haploid cells are produced
Why is meiosis important for sexual reproduction
- Increases genetic variation
- Ensures that resultant zygote is diploid
Asexual reproduction
- Produces genetically identical offspring known as daughter cells (clones)
- Involves mitosis
What is a chromosome
A linear DNA molecule tightly coiled around proteins
Why is mitosis important in gametes
- Asexual Reproduction
- Growth
- Repair of damaged cells
- Cell replacement
Four stages of mitosis
Prophase
Metaphase
Anaphase
Telophase
Gametes in a plant
Pollen- Produced by anther
Ova- Produced in the ovules
Cross pollination
The transfer of pollen from the anther of one flower to the stigma of another plant
Self-Pollination
When the pollen from a flowers anther is deposited on the stigma of the same flower
Insect Pollinated Plant Features
- Stamen enclosed (in flower)
- Stigma is sticky and enclosed
- Petals are bright and colourful
- Nectaries are present to attract insects
Wind Pollinated Plant Features
- Stamen exposed outside plant
- Stigma exposed and feathery to catch pollen
- Petals are small and green
- Nectaries are absent
Sexual Reproduction in plants
- In sexual reproduction, gametes are produced (pollen and ovum)
- Gametes fuse to form a zygote
- The zygote will divide many times by mitosis to form all the cells of the new organism
Plant Fertilisation
- Pollen grains deposited on stigma
- Pollen grain grows a pollen tube which grows down the style
- When tube meets ovule, gametes travel through the tube entering it
- Fuses with ovum and divides by mitosis to form an embryo
What does a plant ovary develop into?
Ovary develops into fruit
What does plant ovule develop into?
Ovule develops into the seed
Seed development
- Zygote develops into embryonic plant with a small root (radicle) and shoot (plumule)
- Other contents develop into a cotyledon
- The ovule wall becomes the seed coat or testa
- The ovary wall becomes the fruit
What is a cotyledon?
A food store for the young plant when it germinates
What is a testa?
The hard coating of the seed
Germination
Plants use their food stores (using enzymes) to use carbohydrates as fuel in respiration until they have a leaf that can photosynthesise
Factors needed for germination
Oxygen - to aerobically respire
Warmth - Optimum temp for enzymes
Water - Activates enzymes
Practical: Investigate the conditions needed for germination
C- Change the abiotic conditions in which the seeds germinate
O- Cress seeds are all taken from same parent plant
R- Repeat the investigation 3 times and take an average
M- Measure how meant seeds in each test tube germinate after a set period of time
S- Control type of water used, Control temp for tubes A, B and C
Asexual reproduction in plants
- Runners
- Tubers
- Bulbs
- Cuttings
- Graphtings
How do runners reproduce
Asexually, a new plant is produced where the runner touches the ground
How do tubers reproduce
Tubers are good stores so one plant can produce many tubers which each grow many shoots to form new plants
How do bulbs reproduce
Asexually, they have underground buds containing stored food. New shoot grows out of parent bulb to form daughter bulb
Cutting
Cut a piece of healthy plant with a few leaves and place in compost where it will continue to grow and develop a new plant
Ovary
Where egg cells are formed by meiosis (in the follicle). Produces the hormone oestrogen and progesterone.
Oviduct
Egg cells travel down this to the uterus. Lined with cilia which move the cell. It’s the site of fertilisation.
Uterus (womb)
A lining forms here where the embryo implants and where the foetus develops (thick muscular wall). Contracts during labour.
Cervix
Narrow opening to the uterus. Dilates during labour to allow baby to come out.
Vagina
Where ans penis is inserted during sexual intercourse and where the baby passes through when born.
Testes
Where sperm cells are formed during meiosis, produces testosterone.
Sperm duct
Maturing sperm pass through this tube
Seminal vesicles and prostate gland
Releases liquid into sperm duct to make semen, provides nutrients for sperm.
Penis
Transports urine and amène out the body. Contains tissue which fills with blood to become erect (helps release semen in sexual intercourse)
Urethra
Tube inside penis which transports urine or semen
Placenta
- Allows the embryo to obtain materials such as oxygen and nutrients (glucose, amino acids, fatty acids and glycerol) (diffusion)
- Allows embryo to get rid of waste (urea and carbon dioxide) (diffusion)
- Anchors the embryo in the uterus
What hormone does the placenta secrete?
Progesterone
Amnion membrane
Encloses the embryo and secretes amniotic fluid which protects the embryo from bumps
Foetus
When the embryo looks human
Why is there no physical connection between the circulatory cells in mother and foetus?
- The mothers blood pressure is much higher
- The mothers blood contains white blood cells that would attack foetal blood
What causes puberty for boys?
Testosterone
Secondary sexual characters for boys
- Voice Breaks
- Sperm Production Begins
- Shoulders Broaden
- Hair Growth
- Muscular Development
- Growth of Genitalia
- Mood Swings and Acne
What causes puberty for girls?
Oestrogen
Secondary sexual characters for girls
- Menstrual Cycle Begins
- Pelvis Broadens
- Hair Growth
- Breasts Develop
- Genitalia Growth
- Mood Swings and Acne
FSH in boys
Stimulates sperm production
LH in boys
instructs testes to produce testosterone (male sex hormone)
Menstrual Cycle: FSH
- Secreted from Pituitary Gland
- Causes a single egg to mature in one of the ovaries inside a follicle
Menstrual Cycle: LH
- Secreted from Pituitary Gland
- Stimulates the release of the egg day 14
Menstrual Cycle: Oestrogen
- Secreted from the ovary
- Causes uterus lining to grow
- Inhibits FSH (no more eggs)
- Stimulates LH
Menstrual Cycle: Progesterone
- Secreted from the ovary
- Maintains the uterus lining
- Inhibits FSH and LH
