Science Form 2 (chaper 3)

3.1 Organisms and Their Claasification

-In Science,living things are called organisms.

-There are millions of different types of organisms living on this planet.

-Biological diversity or in short,biodiversity refers to the variety of different types of living organisms in a particular area.

-Biodiversity is found everywhere around us

-The wide variety of organisms on earth is known as biodiversity or biological diversity



Claasification of organisms
-Scientist estimate that there are about 10 to 100 million kinds of organisms on earth.

-So far,scientists have only discovered about 2 million kinds of organisms

-In order to study this huge diversity of organisms,scientists sort organisms into groups.

-The sorting of organisms into groups is called claasification of organisms.

-They are claasified according to their characteristic

-Two major groups of organisms are – animal and plant

-The claasification of organisms will allow us to remember and relate them to each other

Claasification = the sorting of things into groups compare the similarities and differences among them (when an organisms is put together in the same features or characteristic together)




Common characteristic for claasifiying:
-Habitats
-Warm blooded or cold blooded
-How they move
-Body surface
-Type of respiration
-Reproduction methods



CLAASIFICATION OF ANIMALS
-Animals with the same characteristic features are claasified into the same group and enable us to study them systematically
-They are divide into two groups: invertebrates and vertebrates
-Vertebrates are animals with backbone that protect the spinal cord
-Invertebrates are animals without backbone

Vertebrates Invertebrates
main body support is skeleton (bones) and consist of mainly large animals
main body support are body fluid pressure or exoskeleton and consist of small animals with simple body structure
Some are big and some are microscopic

Can be divide into – mammals, birds, fish, amphibians and reptiles Live in different types of habitats; water, land
Some have many legs and some do not have any
Makes up more than 95% of all animal in the world



Mammal
~warm-blooded
~breathe with lungs
~bodies covered with hair or fur
~reproduce by giving birth to live young
~have their young fed on milk

E.G.
platypus ,cow,whale,bat,monkey

Bird
~warm-blooded
~breathe with lungs
~bodies covered with feathers
~have beaks and wings
~reproduce by laying eggs with shells
~carry out internal fertilisation (体内受精)

E.G.
penguin,eagle,pigeon

Reptiles
~cold-blooded
~breathe with lungs
~bodies covered with dry and scaly skin
~have two pairs of limbs except snakes
~reproduce by laying eggs with shells,on land
~carry out internal fertilisation
~can live both in water and land

E.G
crocodile , tortoise , lizard, snake

Amphibian
~cold-blooded
~breathe through their gills
~bodies covered with smooth and moist skin
~have two pairs of limbs that enable them to move freely
~reproduce by laying jelly-covered eggs without sheels,in water
~can live both in water and land

E.G.
frog, toad, salamander, newt

FISH (Pisces)
~cold-blooded
~breathe through gills
~skin covered with hard protective scales
~have fins and tails to help them swim
~bodies are streamlined so that they canmove fast in the water
~reproduce by laying eggs
~have bodies that are well adapted for life under water

E.G.
seahorse, eel, tuna, clown fish

CL***IFICATION OF PLANTS
Plants are divide into two groups: Flowering and Non- flowering
Flowering plants can divide into two more groups: Monocotyledons and Dicotyledons
Non- flowering plants can divide into three more group: Mosses,Fern and Conifers

Flowering plants
a) Monocotyledons
~Produce seeds with one cotyledon
~Have fibrous root
~The stems are soft and not woody
~The leaves have parallel veins
~Flower parts in threes

b)Dicotyledons
~Produce seeds with two cotyledons
~Have a main root and a lot of branching roots (tap root)
~The stems are hard and woody
~The leaves have a network of veins
~Flower parts in fours or fives

Non-flowering plants
Mosses
~Simple plants with stems and small leaf.
~No roots.
~Live on land and shady places.
~Moss plants are green in colour
~Reproduces : spores grow with in capsules.

Conifers
~Have roots, stems.
~Leaves : needle-like
~Do not produce flowers.
~They produce cones
~Reproduce by seeds produced in the cones.

Ferns
~Have stems, leaves, roots.
~Line on land in moist and shady places
~Reproduce: spores growing in capsules attach on the back of leaves



The importance of biodiversity
A source of food - animals and plants provide different kinds of nutrients
A habitats for living things/ organisms
A source of materials – for construction, handicraft
A source of medicine – extract from various tree
A source of clean water – forest and wetlands act as catchments area
Air to breathe – the exchange of O2 and CO2 during photosynthesis maintains the balance in the air
Aesthetic values – beautifies the natural environment
A source of economic income – ecotourism / recreation
Others – mangrove for coastal protection and wetlands for flood control