YEAR 9 Cells and Control Flashcards
How many pairs of chromosomes in a DIPLOID human cell
23 pairs
46 total
What do chromosomes do
Contain instructions for cell division
Contain genes
What is the order of the 6 stages of MITOSIS
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Explain Interphase
Cell is growing in size
More organelles are formed
DNA is being copied
Why might an organism reproduce ASEXUALLY
Doesn’t need a mate
Conserves energy
Allows populations to grow in isolation
How do cancers grow
Genetic mutation in cells
Cells lose control of cell cycle
Cells divide rapidly
Forms masses of undifferentiated cells
-> TUMOURS
Why are tumours dangerous
Disrupt function of nearby organs
Can deplete nutrients and oxygen
What are the disadvantages of asexual reproduction
Clones are genetically identical
This makes them very vulnerable to being all wiped out by a disease
This also makes the population less able to evolve and adapt
What does it mean if a value lies on the 80th percentile
It is greater than 80% of the values in that data set
Explain prophase
Chromosomes in nucleus condense
Nuclear envelope breaks down
Chromosomes can move freely
Explain metaphase
Centrioles at either side of the cell use spindle fibres to move chromosomes
Chromosomes line up at the middle of the cell (Sister chromatids)
Explain anaphase
Spindle fibres shorten
Sister chromatids split into daughter chromatids
Daughter chromatids are pulled to the edge of the cell
Explain telophase
New nuclear envelope forms around daughter chromatids
This forms 2 daughter nuclei (one at either side of the cell)
What is a zygote
A fertilised egg cell
How do undifferentiated cells become specialised
They Express the genes to give them specialised characteristics
What are plant meristems
Clumps of undifferentiated cells at root and shoot tips
What happens at the zone of elongation in plants
The stem constantly grows longer via cell growth and duplication
Why do meristem cells have so many ribosomes
To produce proteins for growth
How are leaves adapted to perform photosynthesis
Large sf area to volume ratio
Thin to let light pass through
What is the vascular bundle
The xylem and phloem
What does the phloem do
Transports sugars and nutrients FROM leaves
Explain cytokinesis
The cytoplasm separates to produce 2 genetically identical daughter cells
What does the xylem do
Carries water from roots to stem and leaves
Define stimuli
A change in our external environment
What organs does the CNS consist of
Brain
Spinal chord
What are the purposes of mitosis
Growth
Repair
Asexual reproduction
What is the purpose of synapses
Slow down electrical impulse between neurones
Ensure impulse only moves in one direction
Explain how a reflex arc keeps us safe step by step
Pain stimulates receptors
Impulse sent along sensory neurone
Impulse passes through relay neurone
Impulse sent along motor neurone
Impulse reaches effector (muscle/gland)
Which neurone would connect to a muscle cell
Motor
Which neurone would connect to a light receptor cell in the eye
Sensory
