national 5 biology unit 2

mitosis happens to

- produce new cells for growth
- replace damaged cells + tissues
- maintain the diploid chromosome complement

stages of mitosis

- chromosomes duplicate and become visible
- nucleus is broken down
- spindle fibres attach themselves to the middle of the chromosomes and line up along the equator
- spindle fibres pull chromatids apart to opposite ends of the cell
- separated chromatids become chromosomes and new nuclear membranes form around them
- cytoplasm divides and two identical cells are formed

chromatids

strands of duplicated chromosome

equator

middle of the cell where chromosomes line up

spindle fibres

where chromosomes attach to pull the chromatids apart

what is mitosis

the process by which a parent cell divides to make two new daughter cells

stem cells

- are unspecialised cells which divide to self renew
- have potential to become different types of cells
- are involved in growth and repair

specialisation of cells leads to..

the formation of a variety of cells, tissues and organs

a hierarchy exists:

cells -> tissues -> organs -> systems

the nervous system is comprised of two parts:

- central nervous system
- peripheral nervous system

the central nervous system (CNS) consists of:

- the brain
- the spinal cord

the brain contains:

- cerebrum
- cerebellum
- medulla

function of the cerebrum

initiates movement and regulates temperature

function of the cerebellum

sends signals for the body to move

medulla

helps control vital processes - heartbeat, breathing and blood pressure

function of receptors

detect sensory input

function of electrical impulses

carry messages along neurons, chemicals transfer these between neurons and synapses

the three types of neuron are:

sensory, inter and motor

the pathway of an impulse

- receptor detects a stimulus
- sensory neuron sends impulse to inter neuron
- the impulse passes through the inter neuron in the spinal cord
- motor neuron sends impulse to effector
- effector produces a response and the muscle contracts

function of endocrine glands

release hormones into the bloodstream

hormones

chemical messengers which carry messages to target tissues

target cells have

cells with complementary receptor proteins for specific hormones so only that tissue will be affected by these hormones

secretory cell

cell in the gland

very high glucose concentration causes

decreased water concentration of the blood and water diffuses out of the cells by osmosis

very low glucose concentration causes

cells will not receive as much glucose and won’t release as much energy in respiration

increase in blood glucose

pancreas releases more insulin and less glucogen into the blood. liver cells store more glucose from the blood as glycogen.

decrease in blood glucose

pancreases releases less insulin and more glucagon into the blood which is broken down by glycagon to release glucose into the blood.

all cells except gametes are

diploid

gametes

haploid sex cells, only one of each pair of chromosomes in a diploid cell

diploid

normal number of chromosomes in a cell

haploid

half the number of chromosomes in a cell

male gametes are made in

testes in animals, anthers in plants

female gametes are made in

ovaries in animals + plants

male gametes are called

sperm in animals, pollen in plants

female gametes are called

eggs in animals, ovules in plants

fertilisation is

fusion of two haploid gametes to produce a diploid zygote, which divides to form an embryo

discrete variation

- single gene inheritance
- only one gene controls the characteristic

continuous variation

- polygenic gene inheritance
- many genes control the characteristic

gene

section of DNA which does for a protein

allele

form of a gene

phenotype

physical characteristic seen as a result of a gene

genotype

pair of alleles which a person has which controls one characteristic

dominant

an allele always seen in the phenotype if it is present

recessive

an allele only seen in the phenotype if there is no dominant allele present

homozygous

when a genotype has two alleles exactly the same (AA or aa)

heterozygous

when a genotype has two alleles different to each other (Aa)

P1

the genotypes of the parents in a cross

F1

the genotypes of the offspring from a cross

F2

the genotypes of the offspring resulting if two of the F1 offspring were crossed

phenotype ratios among offspring are not always achieved because

fertilisation is random

plant organs

roots, stems and leaves

transport systems in plants

- water enters the roots through osmosis
- water travels through the root tissue by osmosis until it reaches the xylem
- xylem transports the water up the stem to the leaves
- water moves through leaf cells by osmosis and exits the leaf by evaporation

xylem vessels

- dead and contain lignin for support
- transports water and minerals up the stem

transpiration

diffusion of water out of the stomata

process of transpiration

- water moves from xylem to air spaces by osmosis
- it evaporates, forming water vapour
- water diffuses out of stomata
- transpired water vapour is replaced by more water vapour in the leaf
- pull of water and minerals up the xylem

effect of wind speed on transpiration

increased wind speed increases transpiration

effect of humidity on transpiration

increased humidity decreases transpiration

effect of temperature on transpiration

increased temperature increases transpiration

effect of surface on transpiration

increased surface area increases transpiration

effect of light on transpiration

increased light increases transpiration

function of phloem

transports sugar up and down the plant

phloem is made of

sieve tube, sive plate, and companion cell

in mammals blood contains..

plasma, red blood cells, and white blood cells

blood transports

nutrients, oxygen and carbon dioxide

red blood cells are specialised by

- biconcave to increase surface area for diffusion of oxygen
- haemoglobin to bind to oxygen
- no nucleus to make room for haemoglobin

white blood cells

part of the immune system and involved in destroying pathogens

phagocytes

carry out phagocytosis by engulfing pathogens

lymphocytres

produce antibodies which destroy pathogens, each antibody is specific to a particular pathogen

pathway of oxygenated and deoxygenated blood through heart, lungs and body

- blood enters right atrium through vena cava
- contraction of muscular ventricle wall forces blood into pulmonary artery
- this carries blood from heart to lungs
- pulmonary vein returns oxygenated blood from lungs to left atrium
- blood pumped into left ventricle, contraction forces blood into the aorta
- aorta takes blood to all parts of the body
- tissues and organs remove oxygen as blood passes through, deoxygenating it
- deoxygenated blood returns by vena cava to right atrium

heart diagram (right side)

pulmonary artery, vena cava, right atrium, right ventricle

heart diagram (left side)

aorta, pulmonary vein, left atrium, left ventricle

function of vena cava + pulmonary vein

brings blood to the heart

function of right + left atrium

receives blood arriving at the heart

function of right + left ventricle

muscular chamber which pumps blood

function of pulmonary artery + aorta

takes blood away from the heart

destination of blood

lungs and the body

pathway of blood through the heart

cells - veins - vena cava - right atrium - right ventricle - pulmonary artery - lungs - pulmonary vein - left atrium - left ventricle - aorta - body

veins have valves to

reduce backflow of blood

function of coronary arteries

supply heart muscle with oxygenated blood

features of coronary arteries

- carry blood under high pressure
- thick muscular walls
- narrow central channel

features of veins

- carry blood under low pressure
- thin walls
- wide central channel
- valves to reduce backflow of blood

function of capillaries

absorbs glucose

features of capillaries

- thin walls
- large surface area
- form at networks at organs and tissues to allow efficient material exchange

parts of the villus

epithelium, capillary, lacteal

function of lacteal

absorbs fatty acids and glycerol

oxygen and nutrients from food must be absorbed into the bloodstream to be delivered to cells for

respiration

tissues contain capillary networks to

allow material exchange at cellular level

surfaces in the body that care involved with lots of exchange have these features to increase the efficiency of absorption:

- good blood supply to maintain steep diffusion gradient
- large surface areas to maximise diffusion rate
- thin walls to minimise diffusion distance

process of gas exchange in the lungs

- oxygen and carbon dioxide are exchanged in the lungs
- oxygen enters lungs and diffuses through thin cell membranes
- oxygen diffuses into cells
- carbon dioxide produced from respiration diffuses from cells into the bloodstream
- carbon dioxide diffuses through thin cell membranes and is breathed out

gas exchange happens in the

alveoli in the lungs

in the alveoli, the direction of gas movement is

oxygen in, carbon dioxide out

alveoli are adapted for diffusion by having:

- a large surface area
- a good blood supply
- thin walls for efficient diffusion
- are moist

absorption of nutrition occurs in

the small intestine

features of villi

- thin walled
- large surface area
- good blood supply to aid absorption
- surrounded by capillary networks
- contains central lacteal to absorb fatty acids and glycerol

water soluble food products

glucose and amino acids