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B4 B5 B6 Revision B4 The Processes of life B6 Growth and Development B6 Brain and Mind.

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B4 B5 B6 Revision B4 The Processes of life B6 Growth and Development B6 Brain and Mind
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B4 B5 B6 RevisionB4 B5 B6 Revision

B4 The Processes of life

B6 Growth and Development

B6 Brain and Mind

B4 The Processes of life

Features of all living things

Movement

Respiration

Sensitivity

Growth

Reproduction

Excretion

Food

All living things are made

up of cells.

Enzymes are proteins that speed up chemical reactions in cells.

They need a specific constant temperature to work at their optimum.

Enzymes

Enzymes become denatured (stop working) above about 55oC.

The higher the temperature the faster molecules move around and therefore (a) collide more frequently and (b) collide with more energy.

This results in an increased rate of reaction.

click to react

lock and key

enzyme molecule

Most enzymes work best at about 40oC.

active site

The active site can be changed by heating above a certain temperature and altering the pH, so that the molecules can no longer fit and the reaction cannot happen.

Enzymes at work in plants

Photosynthesis equation (takes place in chloroplasts)

light energy

6CO2 + 6H2O C6H12O6 + 6O2

chlorophyll

Carbon dioxide water glucose oxygenChlorophyll absorbs light and uses the energy to kick-start

photosynthesisGlucose is used by plant cells in 3 ways

1. Making other chemicals needed for cell growth

2. Storing energy in starch molecules

3. Releasing energy in respiration

Diffusion (passive transport)

This is the movement of molecules from a region of their high concentration to a region of their lower concentration

Region of high concentration

Region of low concentration

Diffusion causes the molecules to become evenly distributed due to their random movement.

It is like as if the molecules have moved from the region of high concentration to the region of low concentration.

Diffusion in the leaf happens through the stomata- carbon dioxide in and oxygen out

= eg oxygen

Osmosis is the same as diffusion but applies to water molecules passing through a partially permeable membrane.

= starch

= water

High concentration of starch

Low concentration of starch

partially permeable membrane

High concentration of water

Low concentration of water

movement of water molecules Starch molecules cannot pass through the partially permeable membrane but water molecules can.

If too much water passes into a cell by osmosis then it may rupture.

Molecules like glucose are moved by active transport.

cell

low salt concentration

high salt concentration

potato chip

the potato chip absorbs water and expands

the potato chip loses water and shrinks

Osmosis in plant cells

Minerals from the soil

Plants take in nitrogen from the soil as nitrate ions, they

are absorbed by root hair cells.

The cells use a process called active transport to pump

nitrates from the soil and into the roots against their

diffusion gradient.

The rate of photosynthesis

Increasing the amount of light a plant receives increases

the rate of photosynthesis up to a point.

Increasing the light intensity stops having an effect on the

rate of photosynthesis because one of the other factors e.g.

carbon dioxide, water, chlorophyll or temperature is in

short supply. This factor is called the LIMITING FACTOR

Environments and adaptations

A habitat is a place where an organism lives.

A quadrat is used to survey the plants in a

square metre.

The positioning of a quadrat in the area being

investigated is random.

Samples can be taken at regular intervals along

a straight line called a transect.

Energy for life

Aerobic respiration

Glucose + oxygen carbon dioxide + water (+ energy released)

C6H12O6 + 6O2 6CO2 + 6H2O

What happens to the energy from respiration?

• used in active transport

•movement

•building molecules used for growth and repairAnaerobic respiration

Glucose lactic acid (+energy released) – in animals

Glucose ethanol + carbon dioxide (+ energy released)

– in plants and microorganisms

Useful products from respiration

Bioethanol (used to fuel car engines) is made from

sugars in plant material.

Yeast cells take sugars and convert them into ethanol

during the process of anaerobic respiration, this is called

fermentation. Biogas is a fuel obtained from animal manure or human

waste using bacteria, it produces methane gas.

The fuel can be used to heat buildings and run

electricity generators

B4 Homeostasis

B5 Growth and Development

B6 Brain and Mind

B5 Growth and Development

DNA has a double helix structure

Cytoplasm – where proteins are made

Nucleus – where the genes are located

The base pairs always pair up the same way A to T and G to C

adenine

C

T

A

T

G

T

G-

A-

T-

A-

C-

A-

C

T

A

T

G

T

nucleus cytoplasm

The DNA unzips to expose the codeA copy of the code is made using RNAThe mRNA travels to the cytoplasm The DNA zips up againThe mRNA is used to produce a protein

Each gene codes for a specific protein

gene

(using ribosomes)

The order of bases in a gene determines the order of amino acids that make a particular protein.

This is the simplest amino acid - valine

Protein is made up of amino acids joined together in chains

The order of amino acids determines the 3D structure of a particular protein.

The 3D structure of a protein determines its function (job)

Meiosis is a type of cell division that produces gametes, ie sperm and egg cells.

Cells produced by meiosis only contain half the chromosome number of the parent cell

Cell division by mitosis produces two new cells identical to each other and to the parent cell

Cell division

Mitosis involves copying the chromosomes exactly

A zygote divides by mitosis to form an embryo

In a human embryo, up to the eight cell stage, all the cells are identical and could produce any sort of cell required by the organism (embryonic stem cells);

After this point the cells become specialised and form different types of tissue.

Adult and embryonic stem cells have the potential to produce cells needed to replace damaged tissues.

In carefully controlled conditions of mammalian cloning, it is possible to reactivate inactive genes in the nucleus of a body cell to form cells of all tissue types.

Making stem cells using the DNA from a patient means the cells wont be rejected when they are transplanted into the patient

This means that the patient’s immune system wont attack the transplanted stem cells

foreign cell with antigen

White blood cells recognise it as a foreign cell and make antibodies

The antibodies help to kill the

foreign cell

X

With this technique the white blood cells do not recognise the

transplanted stem cells as foreign and therefore don’t attack them

New cells in plants specialise into cells of roots, leaves or flowers.

Some plant cells remain unspecialized and can develop into any type of plant cell, unlike animal cells.

Most plants continue to grow in height and width throughout their lives, unlike animals.

Plant meristems divide to produce cells that result in increased height, length of roots, and girth of the plant. If the hormonal conditions in their environment are changed, unspecialised plant cells can develop into a range of other tissues

Transport vessels: xylem and phloem

Organs: leaves, roots and flowers

Cut stems from a plant can develop roots in the presence of plant hormones (auxins) and grow into a complete plant which is a clone of the parent.

shoot tip

The action of light causes auxin to move across the shoot tip from the side getting the light to the shaded side.

plant stem

This causes the cells on the shaded side to elongate which causes the stem to bend towards the light.

This helps the plant to grow towards the light which helps its survival.

A D C

4

16

DNAcytoplasm

mRNA

amino acids

B4 Homeostasis

B5 Growth and Development

B6 Brain and Mind

Brain and Mind

What are we sensitive to ?

• light

• sound

• pressure

• chemicals

• temperature

• orientation

The 5 senses are:

• sight• hearing• touch

• taste

• smell

eyeear

skin

nose & tongue

nose

The retina contains light sensitive cells

The lens refracts the light to focus on the retina

The retina contains cells called cones which enable colour vision

The Ear

semi-circular canals which sense orientation

The Tongue

The tongue has receptors which are sensitive to chemicals and enable us to taste 4 types of flavours.

The Nose

The nose has receptors which are sensitive to chemicals and enable us to smell and taste.

The Skin

The skin has receptors that are sensitive to touch, pressure and temperature changes.

How the nervous system works

nerve cell

axon

dendrite

neurotransmitter receptor site

synapseacetylcholineThe neurotransmitter diffuses across the

gap

Receptor molecules only bind to specific chemicals, initiating a nerve impulse in the motor neuron.

At the end of a sensory neuron an impulse triggers the release of chemicals into the synapse, which diffuse across and bind to receptor molecules on the membrane of a motor neuron.

stimulus is detected by a receptornerve impulse travels along a sensory neuroneneurotransmitter diffuses across a synapsenerve impulse travels along a relay neurone

neurotransmitter diffuses across a synapse

nerve impulse travels along a neurone to the brain

nerve impulse travels along a motor neuronemuscle contracts / hormone is released from a glandConscious awareness of the stimulus

Sequence

at the same time

receptor

stimulus

central nervous system (brain and spinal cord)

sensory neurone (nerve)

motor neurone (nerve)

effector (muscle or gland)

Fast and short lived responses

nervous systems use electrical impulses

melanin

ADH

ACTH, FSH, LH, growth H

thyroxine

PTH

Involved in producing T cells

adrenalineInsulin, glucagonoestrogen, progesterone

testosterone

Glands in the body

High blood sugar level

insulin released from the

pancreas

decrease in blood

sugar level

Low blood sugar level

glucagon

released from the pancrea

s

increase in blood sugar level

Control of blood sugar

homeostasis

Hormonal control

Hormones are chemicals which travel in the blood

slow and long lasting

How can reflex actions be an advantage for survival ?

A new born baby has a set of reflex actions, eg:

Grasping reflex: Touching a baby’s palm will cause the baby’s fingers to curl.

Sucking reflex: Putting an object in a baby’s mouth will cause the baby to suck the object .

Diving reflex: Putting a baby in water will cause the baby to hold it’s breath and move it’s arms around

Pupil reflex

When the surroundings get darker the iris relaxes causing the pupil to dilate

When the surroundings get lighter the iris contracts causing the pupil to get smaller

This reflex helps to protect the light sensitive receptors in the eye when it is too light and to get more visual information when dark.

Some birds develop a learned conditioned reflex or have an evolved reflex to avoid eating particular caterpillars on the basis of their colours.

Some caterpillars have a poisonous toxin in their skin.

Simple animals rely on reflex actions for the majority of their behaviour

This is a unicellular organism which needs light to survive, eg plankton

This is a reflex response to move towards lighter areas

This is a reflex response to something moving

Light & dry Dark & dry

Dark & moist Light & moist

Woodlouse

A reflex response to move to dark areas enables it to hide from predators

The disadvantage of these simple reflex behaviours is not being able to respond appropriately to new situations.

Eg what if a spider is waiting for the woodlouse in the dark area !

Pavlov’s dog

The final response has no direct connection to the stimulus

A reflex response to a new stimulus can be learned

The brain can modify reflexes

For example, being given a hot plate and instinctively wanting to drop it but yet holding on to it.

in a nut shell !

How the brain works

Microscope slide of neurons in the brain

visual

auditory, speech

spatial sense

essential functions

movement

reasoning

cerebral cortex

The cerebral cortex is the part of our brain most concerned with intelligence, memory, language and consciousness.

CT scanner MRI scanner

PET scanner

A variety of methods can be used to map the brain

CT and MRI scanners can be used to get images of structures.PET scanners can be used to monitor activity in the brain

Electrical stimulation of the brain can be used in studies

MDMA - ecstasy

Ecstasy blocks the re-uptake of serotonin in the synapses of the brain.

This causes an increase in the serotonin concentration which leads to mood-enhancing effects.

During development, the interaction between mammals and their environment results in neuron pathways forming in the brain.Here, neuron pathways in the visual cortex interplay with neuron pathways in the motor cortex in order to grab an object.After many attempts the neuron pathways get fine tuned to produce the responses that we intend.

Eventually we build up a vast array of efficient pathways.

Brain stem

1

2

3

4

The second set of nerve cells are not stimulated enough to fireOne of the nerve cells in the second set receives enough input to fireOne of the nerve cells in the second set receives enough input to fire and this neuronal pathway is strengthened by a nerve impulse from the brain stemThe neuronal pathway doesn’t need the extra input to work

Click 1 then 2 then 3 then 4

This gives you a very basic idea about how neuron pathways are formed

Learning is the result of experience where certain pathways in the brain will become more likely to transmit impulses than others.

This is why some skills may be learnt through repetition.

The variety of potential pathways in the brain makes it possible for animals to adapt to new situations.

There is evidence to suggest that children may only acquire some skills at a particular age, eg language development in feral children.

A feral child is one who has been brought up by wild animals from early childhood.

Memory is basically the storage and retrieval of information.

Verbal memory can be divided into short-term memory and long-term memory.

Humans are more likely to remember information if:

• they can see a pattern in it

• there is repetition of the information, especially over an extended period of time

• there is a strong stimulus associated with it, eg colour, light, smell, sound etc

By the time you have become consciously aware of the snake your brain has already set into play a series of responses.

9/20 x 100

involuntary

A B E C

B4 Homeostasis

B5 Growth and Development

B6 Brain and Mind


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