Topic 1 [Characteristics and Classifications of Living Organisms] 

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[1.1] Characteristics of Living Organisms 

: An by an organism or part of an organism that causes a in position or place. 

: in cells that break down and release for

: The ability to or stimulus in the internal or external environment and to make an appropriate reaction/response. 

: The permanent change in and by an increase in , , or both. 

A process that makes of the same species as their parents. 

: Removal of the of toxic materials, and substances in excess of requirements. 

: Taking in of materials for , , and . 

**Note that the above can be remembered by the acronym .** 

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[1.2] Concept and Use of a Classification System 

As you move down the hierarchy groups, there will be more similarities and less differences between individuals. 

The taxonomic hierarchy can be remembered by the sentence: . 

- Organisms are grouped into different . 

- Several different are grouped into a . 

- Several (plural of genus) are grouped into a . 

- Several into an . 

- Several into a . 

- Several into a . 

- Several into a . 

The naming of species that uses two words. Each name has two parts, the and the . 

Example: 

- Humans belong to the genus Homo, and our species is sapiens, so the scientific name is Homo sapiens

When writing scientific name (Given by Binomial naming system), underline it. When typing it, italicise it. 

:The of biological form and arrangement of the parts of a plant or animal. 

: of the biological structure that make up an organism, either (Something that's big enough to see) or structure. 

Note that organisms that share a ancestor are more closely related, and therefore the DNA sequences are than those that share only a ancestor. (An example would be humans and apes). 

The smallest group at the lowest level in the taxonomic hierarchy. 

> Consists of individuals with a (genetic material of an organism), different from the genome of other species. 

> All of the same species have features (morphological and anatomical). 

> Mature individuals can interbreed to produce . 

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[1.3] Features of Organisms 

The in all living organisms: 

1. Cytoplasm, cell membrane, and DNA 

2. Ribosomes (For protein synthesis)

: 

: 

- Multicellular (Dependant on other organisms for feeding/ Basically means they do not produce their own food/ Eat other living organisms). 

- Divided into two groups: (With backbone) and (Without backbone) 

: 

: 

- Scaly skin (Covered in mucus) for streamlining or reducing resistance while swimming. 

- All live in water. 

- Fins for movement and stability. 

- Operculum (Covering gills for gas exchange)

- - Cold blooded 

: (e.g frogs, salamanders) 

- Moist skin for gas exchange 

- Adults often lives on land, but lay eggs in water 

- The young typically have gills while adults have lungs 

- Wide mouth as adult amphibians are carnivores 

-

: (e.g crocodiles, turtles) 

- Dry scaly skin to limit water loss

- Lay eggs with waterproof shells 

- Tail for swimming (If they can swim) 

- Mouth with teeth and bony ridges for feeing 

-

: 

- Feathers 

- Lay eggs with hard shells 

- Forelimbs have become wings 

- Have beaks

- (Heat comes from within body as a result of respiration) 

: 

- Have hair 

- External ears 

- Give birth to live offspring 

-

**Fun fact: The one thing that defines mammals (All mammals have this trait) is that all mammals have mammary glands (Milk glands). Some mammals lay eggs (Platypus, spiny anteater), but what makes them mammals is that they have mammary glands.** 

: 

- Animals with but without backbones 

- Waterproof

Live on dry land 

Four major groups of arthropods: 

- 3 segmented body; ,,

- 6 legs and 4 wings (With exception, ants and termites don't have wings) 

- Wings and legs are attached to the . 

-

- to sense chemicals in the environment 

: 

- Four pairs of legs 

- 2 segmented body; (Head and body combined in one),

-

-

: 

- Five to seven pairs of legs 

-

- 2 segmented body; ,

- First pair of legs often used as pincers 

- Body covered by hard exoskeleton made out of

- Mainly live in the ocean 

- A pair of green glands excrete wastes near the base of antennae 

: 

- Long thin body 

- Many segments with legs on each segment 

-

- as sense organ 

Under the Animal Kingdom are three other phylums: , , and

: (e.g roundworms)

- Invertebrate 

- Body unsegmented 

- Long cylindrical body, tapered at both ends 

- Body covered with cuticle, tough and flexible 

- Reproduction is sexual 

**Most nematodes are parasitic.** 

: (e.g leeches, earthworms) 

- Invertebrate 

- Many segments on long body 

- Body covered with mucus to conserve water 

- Bristles usually present for movement 

: (e.g snails, clams, squids, slugs, octopus, scallops) 

- Invertebrate 

- Body is soft and unsegmented, consisting of head, muscular foot and visceral mass 

- Shell (Calcium carbonate) might be present 

- Can be marine, freshwater, or terrestrial 

: 

- (They create their own food via photosynthesis) 

- Contain , which is a green, light absorbing pigment.

- Plant cells contain cell walls that are made of

2 major groups of Plants: 

(Non-flowering) 

(Flowering) 

: 

- Strong stem, roots, and leaves 

- Reproduce by

: 

- with bright colours, nice scent etc. to attract pollinators (insects/birds) 

- is large for high rate of photosynthesis 

- to anchor the shoot and absorb water and ions 

that come in specialised shapes, colours, smells, and texture. They are dispersed by wind, water and animals. 

2 major groups of Angiosperms: 

- One seed leaf 

- Parallel veins in leaf 

- Two seed leaf 

- Branched veins in leaf 

: 

- Have nuclei 

- Cell walls are made of chitin (Pronounced kai-tin) 

- (They feed on dead materials) 

- Do not have chlorophyll and do not undergo photosynthesis 

- Reproduction: 

> Unicellular yeast: Asexual reproduction by

> Other fungi: Production of

:

- Very small (Only visible under high-powered microscope) 

- Unicellular/Single-celled organisms 

- No true nucleus 

- Do not contain organelles 

-

- Reproduce by

1. Flagellum: A tail-like structure for swimming 

2. Cell membrane

3. Cell Wall (Is not made of cellulose/chitin) 

4. Cytoplasm: Contain enzymes and food molecules but no organelles 

5. DNA: Circular (Unlike human's double helix) and not contained inside a nucleus 

6. Plasmid: A small ring of DNA 

: 

- All have cells with a nucleus 

- Most are unicellular, although some (Like seaweeds) are multicellular 

- Two major types: 

: With chloroplast and cellulose 

: e.g Amoeba 

- Some feed by photosynthesis while others feed on organic substances made by other organisms 

: 

Virus are not in the five-kingdom classification because: 

1. Viruses do not show the typical features of living things as they do not perform respiration, nutrition, or reproduction unless they are living inside the cells of another living organism/have a host. 

- All viruses are , they cause harm in the form of disease to their host. 

1. Genetic Material: Either DNA or RNA, not both. Genetic material is also always single-stranded. 

2. Protein Coat: To protect the single strand of nucleic acid (DNA/RNA) 

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[1.4] Dichotomous Keys 

: 

- For identification of an unfamiliar organisms 

- Each key has a pair of contrasting features, starting with general characteristics to more specific ones. 

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Leave a vote and comment if this helped you! Disclaimer: I cannot guarantee all the information is correct. I am NOT a professional teacher.

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