Biology Common Entrance

• Variation - The cause of variation is the order of our genes, for example two sisters, one could have ABC and the other sister could have ABB which could be the different head shape or the slight lighter or darker hair shades.
• Environmental variation - Environmental variation is what you choose to do to yourself for example tattoos or piercings. Inherited variation - Inherited variation is what you are born with for example eye color or height.
• Discontinuous and Continuous variation - Continuous variation is when there is a range of variation, for example height. Discontinuous variation is when there is a clear cut-off between two groups, for example blood groups.
• Structure of a flower -

  A) Petal

  B) Anther

  C) Filament

  D) Ovary

  E) Sepal

  F) Style

  G) Stigma

  H) Stem

  
• Seed dispersal - Seeds can be dispersed through animals eating them and then excreting them somewhere else (Zoochory), water carrying seeds away (hydrochory) or being blown away by the wind (anemochory).
• Pollination - Pollen grains from anthers are transferred onto stigmas by insects such as bees or wind.
• Self-pollination - Self-pollination occurs when the pollen lands back on the same flower. It happens because the flower has both male and female parts so they don't need to rely on another flower to get their pollen to the right place.
• Pollination - Pollen from male flowers gets onto female flowers where it fertilises an egg cell inside the ovule. This produces a seed that will grow into a new plant.
• The male reproductive system consists of testicles that produce sperm cells, vas deferens that carries sperm out of the body, seminal vesicle that produces fluid to make up semen, prostate gland that also contributes to making up semen and urethra that transports sperm out of the penis.
• The female reproductive system consists of ovaries that produce eggs, fallopian tubes that carry egg down into uterus, cervix that connects vagina to uterus, uterus where fertilisation takes place and vagina that leads to outside of the body.
• Sexual reproduction involves the fusion of gametes (egg and sperm)
• Cross-pollination - Cross-pollination occurs when the pollen lands on a different flower than the one it came from. The plants have to rely on other plants to transfer their pollen which means they may not always find a suitable partner.
• Cross-pollination - Cross-pollination occurs when the pollen lands on a different flower. This means that it needs to travel further than if it was self-pollinating. The advantage of cross-pollination is that it increases genetic diversity within a species which helps prevent extinction.
• The function of the ovule is to produce eggs. The function of the seed coat is to protect the embryo inside. The function of the endosperm is to store food for the developing plant.
• Sexual reproduction is when two different individuals combine genetic material to create offspring with unique characteristics.
• Fertilisation is when a sperm fuses with an egg to create a zygote which develops into an embryo
• The female reproductive system consists of ovaries that produce eggs, fallopian tubes that carry eggs down towards the uterus, uterus that holds developing embryos, cervix that connects the vagina with the uterus and vagina that allows sperm to enter the uterus.
• Self-pollination - Self-pollination occurs when the pollen lands back on the same flower or another flower of the same type nearby. It does not need to travel far as it can be carried by wind or insects over short distances.
• Fertilisation is when a sperm cell fuses with an egg cell to form a zygote which contains all the genes needed to develop into a baby.