KS3 Biology: Part 3 - Variation and Classification

Variation and Classification

The We classify living organisms into many groups. This is called Genus, which is always capitalised. Species is the name given to organisms that share the same characteristics as other organisms. Species is never capitalized unless it is at the beginning of a sentence. Also if two organisms belong to the same species then it means that would be able to produce fertile offspring together although in some cases the same genus means that they can breed together. An example of this is is a tiger and a lion, which make a liger. The different groups of classification are
-Kingdom
-Phylum
-Chordata
-Animalia
-Felidae
-Genus
-species
A mnemonic to remember this is Kinky Pigs Can Always Fly Going sideways (notice that sideways is not capitalized because species will never be capitalized.

A way of remembering the seven characteristics of living organisms is MRS GREN, Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition.

Variation also exists among species. Variation is the name given to characteristics that differ among species. Different types of Variation are discontinuous and continuous. Discontinuous variation is genetic + environmental, whereas continuous variation is just genetic.

Examples of continuous variation are: shoe size, hand span, tongue rolling and eye colour.

Examples of discontinuous variation are: hair colour, skin colour and a hitchhiker's thumb.


Features we have got in common are: arms and legs, 4 fingers and a thumb on each hand, prominent nose, 2 front facing eyes etc.


Features we have that differ are: skin colour, eye colour and hair colour etc.

Now onto classification of plants and animals...
Plants are split into two groups, which are monocots and dicots.

Animals are known as vertebrates or invertebrates.

The groups of vertebrates are
Birds
Reptiles
Amphibians
Fish
Mammals

The groups of invertebrates are
Echinoderm
Arthropod
Mollusc
Annelid
Cnidaria

Classification keys are ways of classifying animals, whether they are plants or animals, or any type of organism.This is an example of a classification key:
 

KS3 Biology Part 2: Skeletal System

Skeletal System

• The human skeleton has several different functions:

-Support
-Protection
-Movement
-Production of red blood cells

• Joints and Muscles

-Bones in the skeleton are held together in joints.
-Joints allow the skeleton to move.
-Joints are held together by ligaments.
-The end of each bone is covered in cartilage for a smooth surface that cushions the joint.
-The joint is filled with a fluid that lubricates the joint.

• Muscles and Force

-Muscles move joints.
-Muscles are attached to bones by tendons.
-End joint needs two muscles to make it work. This is called an antagonistic pair.
-One muscle moves the joint in one direction. The other moves the joint in the opposite direction.
-Muscles work by contracting and getting shorter in length. This pulls the bone and moves the joint.
-The force exerted by the muscles can be measured in Newtons.
-To work out the force applied by a muscle multiply the mass lifted by its distance from the joint.
-The answer is mass x distance from joint equals force x distance from the same joint.

KS3 Biology Part 1: Cells - the basic building blocks of life

Cells

• Cells make up tissues, which make up organs, and then systems and finally, last but not least systems make up organisms.

There are many parts of cells, which have different functions, examples of these are:
-Vacuole - Stores food and water, inflates the cell like air pumped into a tyre and provides support to the cell.
-Mitochondria - Release energy from food (glucose) by aerobic respiration.
-Chloroplast - Contains green chlorophyll that changes sunlight energy into glucose food energy by a process called photosynthesis.
-Cytoplasm - Where chemical reactions take place like photosynthesis.
-Membrane - Controls what substances enter and leave a cell.
-Cell wall - Made from cellulose and gives rigid support to the cell.
-Nucleus - Stores information and controls what happens inside the cell.

• Now some cell key words....

-Euglena has a long whip-like structure that helps it move through water
-Amoeba can make finger-like projections to help it catch food
-Unicellular organisms have just one cell

• Reproduction in humans

-Reproduction in females involves males and females.
-Males produce sperm cells in the testes.
-Females produce egg cells in the ovary.
-The penis deposits the sperm into the female vagina.
-Sperm swim up through the uterus to the oviduct.
-Fertilisation occurs when a sperm cell joins with an egg cell.
-The fertilised egg then grows into an embryo and eventually becomes a baby.

• Gestation

-Gestation is the period of the embryo developing in the womb.
- Females have a menstrual cycle every lasting for about 28 days. This is called menstruation.
-The growing baby receives food and oxygen from the mother's blood through the placenta and the umbilical cord.
-Therefore, if the mother smokes and drinks alcohol the baby will receive some of the alcohol and nicotine.
-In humans, gestation ends after nine months with the birth of the baby.