Unit 2 - Multicellular Organisms Flashcards
how many chromosomes are in the human body
46 chromosomes or 23 pairs
what type of cells are diploid
cells with two sets of chromosomes
what type of cells are haploid
cells with one set of chromosome
what is mitosis
mitosis is the process of a nucleus dividing into two daughter nuclei, each which have the same amount of chromosomes as the original.
why do cells perform mitosis
mitosis provides new cells for growth and repair of damaged cells whilst maintaining diploid chromosome compliment.
what are the steps of mitosis
- chromosome replicates to form two identical chromatids joined by a centromere.
- the nuclear membrane disappears and spindle fibres form.
- each chromosome becomes attached by its centromere to one of the spindle fibres at the equator.
- the spindle fibres contract causing the centromere to split and one chromatid from each pair moves to opposite poles.
- a nuclear membrane forms around each group of chromatids completing nuclear division.
- division of the cytoplasm forms two identical daughter nuclei
- each new cell undergoes a period of cell growth
what does the central nervous system (CNS) consist of
The Brain and Spinal Cord and other nerves
whats that bit of the brain thats hanging off of the end
cerebellum
long bit on the bottom of the brain
medulla
top of the brain
cerebrum
what does the medulla control
it controls the rate of breathing and heart rate
what carries information around the body to the CNS
Sensory Nerves
what carries impulses from the CNS to the effectors
Motor Nerves
what are the three types of neurons and their position in the body
sensory neuron - from the receptors to the CNS
inter neuron - within the CNS
motor neuron - from the CNS to the effector
what is the correct order of neurons in a reflex arc
stimulus, sensory neuron, inter neuron, motor neuron, effector.
what is a synapse
a synapse is a tiny space between the axon ending and sensory ending between two neurons
what happens when an impulse reaches a synapse
chemicals diffuse across the synapse between two neurons this triggers an impulse at the sensory end of the neuron
what is a reflex action
a reflex action is a rapid, automatic involuntary response to a stimulus.
what are hormones
a hormone is a chemical messenger secreted directly into the bloodstream endocrine glands
what is a target tissue
a target tissue is a group of cells that have complementary receptor proteins for specific hormones.
how does the body regulate blood glucose levels
the body uses the liver as a storehouse, it can store up to 100g of glucose converted into glycogen which can be added or removed depending on supply and demand
where is insulin produced
the pancreas
what catalyses the glucose to glycogen reaction
insulin
where is glucagon produced
the pancreas
what is the function of glucagon
glucagon activates the conversion of glycogen to glucose
when blood sugar levels drop what hormone is released from where
glucagon from the pancreas
when blood sugar level rises what hormone is released and from where
insulin from the pancreas
what type of cells are gametes
haploid they are also the body’s sex cell
what happens during sexual reproduction
the fusion of two gamete nuclei to produce a diploid zygote which divides to form an embryo.
what is the site of sperm production
the testes
site of egg production
the ovaries
what are the steps leading to fertilisation
- an egg is released from the ovary
- the egg is then picked up from the oviduct by cilia
- egg is moved along the oviduct by the hair-like cilia
- the sperm cell will then fertilise the egg
what is variation
variation is the word used when describing differences in a species which are not physical accidents
what are the two types of variation
Discreet Variation and Continuous Variation
what is the difference between continuous and discreet variation
discreet variation cant be measured whereas continuous variation can
give examples of discreet variation
hair color, eye color, weight
give examples of continuous variation
height, shoe size,
what factors effect discreet variation
inherited characteristics (genes)
what factors effect continuous variation
environmental factors
what is a phenotype
the outward appearance of a gene
what is a genotype
genetic information passed on from generation to generation
what make up a gene
alleles
