Section 7 - Reproduction and Inheritance Flashcards
What are the male and female structures in flowering plants? (2)
Male - Stamen Female - Carpel
What does the stamen consist of; and what do the parts do? (4)
Anther - contains pollen grains; which produce male gametes Filament - stalk that supports the anther
What does the carpel consist of; and what do the parts do? (6)
Stigma - End bit that pollen grains attach to Style - Rod like section that supports the stigma Ovary - Contains female gametes (eggs)
What is pollination? (2)
- Transfer of pollen from an anther to a stigma - So that the male gametes can fertilise the female gametes in sexual reproduction
What is cross-pollination? (3)
- A type of sexual reproduction - Where pollen is transferred from the anther of one plant to the stigma of another - Plants that rely on cross pollination rely on things like insects or the wind to help them pollinate
How are plants adapted for insect pollination? (4)
- Brightly coloured petals : to attract insects - Scented flowers and nectaries : to attract insects - Big sticky pollen grains : the grains stick to insects as they go from plant to plant - Sticky stigma : so any pollen picked up by insects on other plants will stick to the stigma
How are plants adapted for wind pollination? (5)
- Small, dull petals : to not attract insects - No nectaries or strong scents : to not attract insects - A lot of pollen grains : small and light, to be carried by the wind - Long filaments that hang the anthers outside the flower : so that a lot of pollen gets blown away by the wind - Large and feathery stigma : to catch pollen as it’s passed away, which often hangs outside the flower
How does fertilisation happen in plants? (4)
- A pollen grain lands on the stigma of a flower, usually with help from insects or the wind - A pollen tube grows out of the pollen grain and down through the style to the ovary - A nucleus from the male gamete moves down the tube to join with a female gamete in the ovary
What are the right conditions for germination; and what will seeds do if the conditions aren’t right? (4)
- Water : to activate the enzymes that break down the food reserves in the seed - Oxygen : For respiration, which provides the energy for growth - A suitable temperature : For the enzymes inside the seed to work, depends on what type of seed - Seeds will lie dormant until the conditions around it are right for germination
Advantages and disadvantages of taking cuttings from plants (3)
- AD : plants can be produced quickly and cheaply
- AD : You can be sure of their characteristics
- DIS : lack of genetic variation; expossure to disease or changes in environmental conditions, all of them will be affected.
What is insect pollination (3)
- Transfer of pollen
- from anther to stigma
- by insects
Give an example of artifical asexual reproduction in plants (3)
- Gardeners use cuttings
- Take cuttings from good parent plants
- Plant them to produce clones of the parent plant
Give an example of natural asexual reproduction in plants (6)
- Strawberry plants
- Parent strawberry plant sends out runners
- Runners are fast growing stems that grow out sideways, just above the ground
- Runners take root at various points a short distance away
- New plants start to grow
- Genetically identical
Describe the process of germination (5)
- Germination can only take place if conditions are suitable, water, oxygen, temperature
- Seed takes in water and starts to grow using its store of energy
- The first root starts to grow down into the soil
- The shoot grows up
- Extra roots grow and the first green leaves appear
How do germinating seeds get energy? (3)
- When a seed starts to germinate, it gets glucose for respiration from its own food store - This gives it the energy it needs to grow - Once the plant has grown enough to produce green leaves, it can get food for energy from photosyenthesis
Explain how a plants leaf mesophyll tissue being eaten affects the growth of the plant (3)
- Less surface area to absorb sunlight
- Less chloroplasts
- Less light, less photosyenthesis
Describe what is meant by the term insect-pollination (2)
- transfer of pollen by insect - from anther/stamen to stigma
Give two ways in which the structure of a wind pollinated flower would differ from an insect pollinated flower (4)
- less bright and smaller petals
- stamens/anthers outside flower
- no nectary
- stigma feathery
Are human body cells haploid or diploid, and what does this mean (2)
- Diploid
- Two copies of each chromosome, arranged in pairs
How many chromosomes does a human cell nucleas contain, and what is the diploid number for a human (2)
- 46 chromosomes
- Diploid number 46
What is DNA (1)
- Long list of instructions on how to put an organism together and make it work
What is a gene (2)
- Found inside DNA molecules
- Genes are chemical instructions that code for a particular protein
Why are proteins important (2)
- Control most processes in the body
- Determine inherited characteristics e.g eye colour
Describe a DNA molecule (7)
- Has two strands coiled together
- In the shape of a double helix
- Two strands are held together by bases
- Adenine (A) Cytosine (C) Guanine (G) Thymine (T)
- Bases are paired A-T and C-G
- This is called complementary base pairing
- DNA is a type of nucleic acid
What are the 4 bases and how are they paired (5)
- Adenine
- Guanine
- Thymine
- Cytosine
- A,T and G,C
Name 2 organisms that reproduce asexually, and what is this type of reproduction called (3)
- Bacteria
- Plants
- Mitosis
What is asexual reproduction (3)
- Involves only one parent
- Offspring have identical genes to the parent
- No variation between offspring and parent
What is mitosis (3)
- When a cell reproduces itself
- By splitting to form two cells
- with identical sets of chromosomes
What is the second step of mitosis (3)
- If the cell gets the signal to divide, it needs to duplicate its DNA
- DNA formes X shaped chromosomes
- Each arm of the chromosomes is an exact duplicate of the other
What is the third step of mitosis (3)
- Chromosomes then line up at the centre of the cell
- cell fibres pull them apart
- two arms of each chromosome go to opposite ends of the cell
What is the fourth step of mitosis (2)
- Membranes form around each of sets of chromosomes
- These become the nuclei of the two new cells
What is the final step of mitosis (3)
- Cytoplasm divides
- Now have two new cells containing exactly the same DNA
- Genetically identical
Apart from asexual reproduction, name two uses for mitosis (2)
- How all plants and animals grow and repair damaged tissue
- Cloning
What is sexual reproduction (3)
- Fusion of male and female gametes
- Offspring contain a mixture of parents genes
- Two parents
What are gametes and how are they produced (3)
- Produced in sexual reproduction
- Sperm cells
- Egg cells
Are gametes haploid or diploid and what does this mean (2)
- Haploid
- In humans, each gamete contains 23 chromosomes
What happens at fertilisation (sexual reproduction) (3)
- Male gamete fuses with a female gamete
- Forms a zygote (fertilised egg)
- Zygote ends up with a full set of chromosomes
After a zygote is formed, what happens to it (2)
- Undergoes cell division by mitosis
- Develops into an embryo
Where does meiosis happen in humans (2)
- Reproductive organs
- Ovaries and testes
Meiosis produces …………….. cells whose chromosomes are …………. (2)
- four haploid
- not identical
What is the first step of meiosis (3)
- Cell duplicates DNA before dividing
- One arm of each chromosome is an exact copy of the other arm
- In the first division of meiosis, chromosomes line up in pairs in the centre of the cell
What is the second step of meiosis (4)
- Pairs of chromosomes pulled apart
- So each new cell has one copy of each chromosome
- Some of the fathers/mothers chromosomes go into each new cell
- Each new cell will have a mixture of f/m chromosomes, creating variation
What is the final step of meiosis (5)
- Second division, chromosomes line up in the centre of the cell
- Arms of the chromosomes are pulled apart
- Left with 4 haploid gametes
- Each only has a single set of chromosomes
- Gametes are genetically different
Outline 3 differences between mitosis and meiosis (3)
- Mitosis : no varation between parent offspring, meiosis, variation (mixture of parents genes)
- Mitosis : one parent, meiosis, two parents
- Mitosis : one round of genetic seperation, meiosis, two rounds
