Classification (2.1 & 2.2)

2.1 Concept and use classification system:

1. Understand that organisms can be classified by the features they share 

2. Describe a group of organisms that can reproduce to produce fertile offspring 

3. Describe the binomial system of naming species as an internationally agreed-upon system in which the scientific name of an organism is made up of two parts, showing the genus and species 

The genus name comes first and then species [always capitalised]. Example homo Sapiens 

2.2 Features of organisms 

1. State the main features used to place all organisms into one of the five kingdoms: Animal, Plant, Fungus, Prokaryote, Protoctist 

Animal: multicellular, Eukaryotic [completecell], have a nucleus, no cell wall, non-chlorophyllous, heterotrophs, feed by ingestion

Plant: Multicellular, eukaryotic, contain a nucleus, contain a cell wall [cellulose], chlorophyllous, autotrophs, feed by photosynthesis 

Fungus: multicellular, eukaryotic, have a nucleus, contain a cell wall [chitin], non-chlorophylllic, heterotrophs, feed by absorption

Prokaryote: unicellular, incomplete cell, no true nucleus or DNA, has a cell wall

Protoctista: unicellular, eukaryotic, have a nucleus, have a cell wall 

2. State the main features used to place organisms into groups within the animal kingdom, limited to: 

(a) The main groups of vertebrates: 

Mammals: Skin is covered with fur/hair. Highly developed lungs with a large number of alveoli, diaphragm are also present. Movement through bony legs. Fertilisation is internal. The female gives birth to young ones, which are fed through the mammary glands. Warm-blooded, highly developed 4-chamber heart and double circulatory system, a pair of external ears 

Birds: Skin and body covered with feathers, scales on legs, lungs with an additional pair of air sacs [helps in long flights]. 4 limbs, but the forelimbs are modified to form wings. The feet have four toes with claws, which help the bird to perch, scratch for seeds or capture prey, according to the species. Fertilisation is internal and the female lays hard-shelled eggs. Warm-blooded. The upper and lower jaws are extended to form a beak, which is used for feeding in various ways 

Reptiles: rough, thick, and large dry scales [helps reduce water loss], respiration through lungs or air sacs, 4 limbs with 5 toes [except snakes]. Fertilisation is internal and the female lays the eggs. Eggs are large with a thick, rubbery shell. Cold-blooded 

Amphibians: smooth, slippery skin, thin and non-scaly skin, respiration through gills [in the early part of life when they live in water]and lungs [later part of life when they live on land] Amphibians have moist skin with a good supply of capillaries, which can exchange oxygen and carbon dioxide with the air or water. Most organisms have four legs [the hind feet have a web of skin between the toes, which helps provide a large surface area to push against the water when the animal is swimming]. External fertilisation. cold-blooded. carnivorous 

Fish: shiny, slippery skin, large number of wet overlapping scales, respire through filamentous gills [gills are protected by a bony plate called operculum], streamlined body and fins to help in the easy movement through water. External fertilisation [the female lays eggs and the male sheds sperm on them after they have been laid], cold-blooded 

(b) The main groups of arthropods: 

Myriapods: have an exoskeleton, no compound eyes pair of antennae, a head, and a highly segmented body with 1 or 2 pairs of legs on each segment. Millipedes are herbivorous. Centipedes are carnivorous.

Insects: have an exoskeleton pair of compound eyes pair of antennae 3 regions in the body, 3 pairs of legs, with 1 or 2 pairs of wings

Arachnids: have an exoskeleton, many pairs of simple eyes pair of antennae, 2 segments [cephalothorax and head], 4 pairs of limbs on the cephalothorax pair of pedipalps [ one used for reproduction and the other used to pierce their prey and paralyse it with poison] 

Crustaceans: have an exoskeleton pair of compound eyes [which have hundreds of separate lenses, and have light-sensitive cells beneath them. Very sensitive to motion and can form simple images] A pair of antennae [sensitive to touch and chemicals], 3 regions [head, thoraxabdomen], 4 or 5 pairs of jointed legs [the first pair usually modified to form special mouth eating parts ] 

3. State the main features used to place organisms into groups within the plant kingdom, limited to ferns and flowering plants(dicotyledons and monocotyledons):

Flowering plants 

Reproduces sexually through flowers and seeds. 

Seeds are produced inside the ovary found at the base of the flower. 

Can be divided into two groups – monocotyledons and dicotyledons 

How to distinguish between monocotyledons and dicotyledons: 

FLOWERS: Flowers from monocotyledons contain petals in multiples of 3. Flowers from dicotyledons contain petals in multiples of 4 or 5 2. 

LEAVES: Leaves from monocotyledons have parallel leaf veins and are long and narrow. Leaves from dicotyledons have reticulated leaf veins (meaning that they are all interconnected and form a web-like network throughout the leaf)and are broad. 

4. Classify organisms using the features identified in 2.2.1, 2.2.2 and 2.2.3 

5. State the main features of viruses, limited to the protein coat and the genetic material 

Nucleic Acid [DNA or RNA - never both] 

Nucleic acid surrounded by a protein coat [capsid]

Some viruses have another layer called viral envelope 

6. Understand that viruses can only replicate in living cells 

Credits: Notes compiled by Manahil Naeem of Karachi Grammar School