Multicellular Organisms Combined

What is a cell?

the basic unit of life

What are the two types of cells?

multicellular and unicellular

What is a multicellular organism?

an organism made of many cells

What is an unicellular organism?

an organism made up of one cell.

How many cell types do multicellular organisms have?

more than one cell type

What are multicellular organisms made up of?

tissues and organs

What is a tissue?

a group of similar cells that work together to carry out a particular function

What is an organ?

a group of different tissues that work together to perform a certain function

The cells in organs are _______________ for their ____________ and work ____________ to form ______________

• specialised
• function
• together
• systems

What is a system?

a group of organs that work together to carry out a particular function

What does the specialisation of cells lead to?

The formation of a variety of cells, tissues and organs

The hierarchy of cells organs system and tissues?

cells —> tissues —> organs —> systems

What is mitosis?

mitosis is a type of cell division in which a diploid body cell copies itself and finally divides into two identical diploid daughter cells

In which cells does mitosis take place?

animal and plant cells

First stage of mitosis?

mitosis starts off with a diploid parent cell. The individual chromosomes coil up and become visible

Second stage of mitosis

each chromosome is replicated so that an exact copy of each chromosome is made. The chromosomes consist of two chromatids joined together by a centromere.

Third stage of mitosis?

The chromosomes line up at the equator (centre) of the cell, and spindle fibres attach to each pair of chromatids

Fourth stage of mitosis?

the spindle fibres shorten, pulling the chromatids apart to form new chromosomes which move towards the opposite poles of the cell.

Fifth stage of mitosis?

the nuclear membranes re-form around each group of new chromosomes and the cytoplasm divides

Sixth stage of mitosis?

two new daughter cells are produced each with the same number of chromosomes as the original

Mitosis provides new cells for

- growth and repair of damaged cells
- replacement of dead or damaged cells

What does mitosis maintain?

the diploid chromosome complement

What is a chromatid?

replicated copy of a chromosome during mitosis

What is a diploid cell?

describes a cell containing two sets of chromosomes

What is the equator of a cell?

middle of the cell

What is a haploid cell?

describes a cell with a single set of chromosomes

What are spindle fibers?

protein threads produced during mitosis that separate the chromatids and transport the chromosomes to the poles

What are stem cells?

unspecialised cells which can divide in order to self-renew.

What do stem cells have the potential to become?

different cell types

What are stem cells involved in?

growth and repair

How can stem cells be obtained?

from the embryo at a very early stage

Where are tissue stem cells found?

can be found in the body throughout life

What does the CNS consist of?

brain and spinal cord

What are the 3 main parts of the brain?

cerebrum, cerebellum, medulla

What is the function of the cerebrum?

responsible for controlling conscious thoughts, reasoning, memory and emotions

What is the function of the cerebellum?

responsible for controlling

balance and co-ordination

What is the function of the medulla?

responsible for controlling breathing and heart rate

What are the 3 types of neurons?

sensory neurons, motor neurons, interneurons

Function of sensory neurons?

carries electrical impulses from sensory receptors to the CNS

Function of inter neurons?

carries electrical impulses from sensory neurons to motor neurons

function of motor neurons?

carries electrical impulses from the CNS to an effector (muscle or gland)

What are receptors?

cells that detect sensory input/ stimuli

What is a stimulus?

a change in the environment

Describe 2 possible responses to a stimulus?

A response to a stimulus can be a rapid action from a muscle or a slower response from a gland

function of electrical impulses ?

carry messages along neurons

What are synapses?

tiny gaps between neurons

What are neurotransmitters?

chemical messengers that cross the synaptic gaps between neurons

What is a reflex arc?

The pathway of information from a sensory neuron through an inter neuron to a motor neuron

Reflex arc description

1) The sense organs contain sensory receptor cells which detect stimuli from the surroundings which triggers an electrical impulse

2) The impulse passes along the sensory neuron, which passes this information to the CNS.

3) Inter neurons operate within the CNS, which processes the information from the senses that require a response.

4) An electrical impulse is then sent along a motor neuron to enable a response to occur at an effector (muscle or gland).

What do reflexes do?

protect the body from harm

What are hormones?

chemical messengers

What do endocrine glands do?

release hormones into the bloodstream

Example of endocrine glands

ovaries,testes and pancreas

Specific hormones are transported _______________?

to target tissues in order to stimulate a response

What are target tissues?

tissues that have cells with complementary receptor proteins for specific hormones

What are blood glucose concentrations regulated by?

insulin and glucagon

where are insulin and glucagon produced?

pancreas

where are the target cells for insulin and glucagon found?

in the liver

What reaction does insulin activate the enzyme for?

converts glucose ---> glycogen

What is glycogen stored as?

carbohydrate

Describe what happens when their is a n increase in blood glucose levels

1) Receptors in the pancreas detect the INCREASE in glucose levels

2) The pancreas responds by producing the hormone insulin

3) Insulin is carried in the bloodstream to the liver

4) The liver cells are stimulated to convert glucose to glycogen (a storage carbohydrate)

5) This causes a DECREASE in blood glucose levels.

Describe what happens when their is a decrease in blood glucose levels

1) Receptors in the pancreas detect the DECREASE in glucose levels

2)The pancreas responds by producing the hormone glucagon

3) Glucagon is carried in the bloodstream to the liver

4) The liver cells are stimulated to break down glycogen to glucose

5) This causes an INCREASE in blood glucose levels

What is sexual reproduction?

reproduction involving combining genetic information from two individuals to produce offspring

The bodies of animals and plants contain?

body cells and gametes

The body cells of most animals and plants contain?

two sets of chromosomes

Cells that have two sets of chromosomes are said to be?

diploid

A gamete sex cell contains ?

one set of chromosomes

Cells that have one set of chromosomes are said to be?

haploid

What is the male gamete in animals called ?

sperm cell

What organs produce the male gamete in animals?

testes

What is the female gamete in animals?

egg cells

What organ produces the female gametes in animals?

ovaries

Where are egg cells released into?

oviducts

What is the male gamete in plant cells called?

pollen grains

Where are male gametes produced in plants ?

anther

What is the female gamete in plants called ?

ovules

Where are female gametes produced in plants ?

ovary

What is fertilisation?

the fusion of the nuclei of the haploid gametes to produce a diploid zygote which divides to form an embryo

What is variation?

any difference between individuals of the same species.

Combining genes from two parents contributes to ?

variation within a species

What is discrete variation?

the single gene inheritance of characteristics where measurements fall into distinct groups

What is continous variation?

the polygenic inheritance of characteristics where there is a range of values from one extreme to the other

What is the meaning of the word polygenic?

type of inheritance involving several genes acting together

Examples of discrete variation?

blood type, hair colour, eye colour, skin colour

Examples of continuous variation?

height and weight

What is a gene?

a section of DNA that codes for a protein

What is an allele?

Different forms of a gene

What is a genotype?

An individual's alleles for a particular characteristic

What is a phenotype?

The physical appearance expressed by an organisms due to their genotype

What is the meaning of heterozygous?

Two different alleles of a genotype

What is the meaning of homozygous?

Two alleles the same for a genotype

What is the meaning of Dominant?

The form of a gene which is always expressed

What is the meaning of recessive?

The form of a gene which will only be expressed if the genotype is homozygous

Why are predicted phenotype ratios among offspring not always achieved?

because of the random nature of fertilisation and the fusion of the genetic information in gametes

Why are xylems lignified?

to withstand the pressure changes as water moves through the plant

Process of transpiration

1) Water is taken into the root hairs from the soil via osmosis

2) Water is then transported through the plant through the xylem tubes

3) Finally, water is lost to the atmosphere by evaporation through the open stomata in the leaf

What is the function of the spongy mesophyll?

cells surrounded by air spaces to allow gases to circulate in the leaf and reach leaf cells

What is the function of the leaf vein?

contains xylem and phloem, which allows water and sugar to be transported into and out of the leaf

What is the function of the lower epidermis?

contains guard cells, which form tiny pores called stomata which allow gases to pass in and out of the leaf

What is lignin?

material that lines the xylem vessel providing strength and support.