Classification

Living organism
- composed of cell
Function / characters of living organisms
- Metabolism
- The web of all enzymes - catalyzed reactions in a cell or organism. ex)
respiration
- Response
- Living things can respond to and interact with the environment
- Homeostasis
- The maintenance and regulation of internal cell conditions. ex) water,
pH
- Growth
- Living things can grow or change size or shape
- Excretion
- The removal of metabolic waste
- Reproduction
- Living things produce offspring, either sexually or asexually
- Nutrition
- Feeding by either the synthesis of organic molecules or the absorption
of organic matter. ex) photosynthesis

Classification of living organism

- classification
- Grouping of organisms into categories on the basis of evolutionary or
structural relationships between them
- only for living organism
Taxon
- is a group of one or more population sof an organism or organisms seen by
taxonomists to orm a unit
- Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
- going up hierarchy, the taxa include larger number of species, but fewer
features

Artificial or natural classification

● Artificial
○ classified by physical traits → developed from ancestors
● Natural
○ classified by species evolved based on DNA or protein
○ should have common ancestor

Advantages of natural classification

- easier to identify species → usually DNA
 - they inherit similar characteristics → prediction of the characteristics of
species within a group

Binomial system
- scientific names
- international name of a species consists of two words
- first name: genus name
- second name: species / specific name
● rules
○ the genus name begin with capital letter, species name with small letter
○ printed text: binomial in italics and underlined

IGCSE Chapter 1.2 Domain & Kingdom 1st Dec

Domain
- Archaea (referred to as archaea)
- Eubacteria (referred to as eubacteria)
- Eukaryota (referred to as eukaryota)
● usually classify as eukaryotes and prokaryotes (nuclei 유무)
○ archaeans and bacteria → prokaryotes

Archaea
- prokaryotes
- can live in an extreme environment. (bacteria cannot)
- some of the archaea can produce methane
*still establishing*

Eubacteria
- prokaryotes
- Have cell structure
- not able to live in extreme environment, widely found in daily life
- nucleoid
- Example: E. coli

Prokaryote
 - archaeans and bacteria
- often unicellular organism
- no nuclei
- cell wall not plant cell wall

Eukaryota
- complex cell structure (having organelles)
- animal and plant cell
- also called eukaryote

Kingdom
- five kingdom of life
- domain of Eukaryota
- animal
- Plant
- fungi
- protista
- domain of Eubacteria
- monera

Animal
- easily recognized kingdom
- multicellular organism
- yes nuclei, no chloroplast
- feed on other organisms
Plant
- easily recognized kingdom
- multicellular
- have nuclei and cell wall made of cellulose
- most have chloroplast
- feed by photosynthesis
- may have structures like root, stem and leaves

Fungi
- ex) mushroom, yeast, penicillin
- usually multicellular
- have nuclei, cell wall not made of cellulose
- no chloroplast, but saprotroph (decomposer)

Protista
- for all remaining living organism
- both multi and unicellular
- have nuclei
- may or may not have cell wall or chloroplast
- feed by photosynthesis or on other organisms
- ex) paramecium
Virus - non living organism
- no cell structure
- cannot do anything other than just exist until they get inside a living cell

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IGCSE Chapter 1.3: Kingdom, Phylum, and class
difference in physical change can be evidence for classification them into one taxon.
How to see the differences and similarities in the classification
- for the natural classification, scientists depend on DNA research to show relation
between species
- Species in one taxa can show the similarities in many aspects
- For some of the physical traits, they can be an evidence for classifying them into one
taxon
number Phylum Symmetry Segmentation Mouth / other example animal
anus

1. Porifera no / no porous surface, sponge

symmetry cannot move

2. Cnidaria radial / have - tentacles with jellyfish and

symmetry mouth but stinging cells coral reef
no anus - soft but for
hard corals,
they secret
CaCO3 to form
the hard shell

3. platyhelmint bilateral / have - flat and thin flatworms and

hes symmetry mouth but bodies in the flukes
no anus shape of a
ribbon
- all soft,
without the
skeleton

4. Mollusca bilateral non-visible both have most have shell snails, octopus
symmetry mouth and made of CaCO3 and oyster
anus soft body

5. Annelida bilateral ring-shaped both have ring-shaped leech and

symmetry segments mouth and very segments, earthworm
anus often with
bristle

6. Arthropoda bilateral segmented both mouth appendages insects, lobsters,

symmetry bodies and and anus with joints crabs
legs between
sections

7. Chordata bilateral segmented both mouth notochord and human, fish,

(Vertebrate) symmetry bodies and anus hollow dorsal birds
nerve curve

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Chordata
- Mammals
- Birds
- Reptiles
- Amphibians
- Fish
 Limbs, legs Gas Exchange Reproduction Body
temperature

Mammal Human/bat 4 pentadactyl Lungs with Internal Maintain

limbs. 5 fingers alveoli, fertilization, give constant body
alveolus birth to young temperature

Bird Songbird 4 pentadactyl Lungs with Internal Maintain

limbs, 2 limbs perabronchial fertilization, hard constant body
modified as tubes shells around temperature
wings exchange for the eggs
two times

Reptile Veiled 4 pentadactyl Lungs with Internal Don’t maintain

chameleon/turtle limbs extensive fertilization, soft constant body
folding shells around temperature
eggs

Amphibian Chinese giant 4 pentadactyl Simple lungs External Don’t maintain

salamander / limbs with small fertilization in constant body
frog internal folds water, protective temperature.
and moist jelly around
surfaces eggs
Larval stage
lives in water

Fish Clownfish Fin Gill slit External Don’t maintain

fertilization constant body
temperature.

Phyla in the plant

- Bryophyta - mosses
- Filicinophyta - ferns
- Coniferophyta - conifers
- Angiospermophyta - flowering plants - lemon Citrus limon.

Leaves Roots Stems Vascular Reproduction

tissue

Bryophyta Yes, simple No, Rhizoids yes, only None, Spores, asexual
structure (two simple directly reproduction.
vascular structure absorb water
tissue) from
environment

Filicinophyta Yes Yes Yes, Yes Spores, either

non-woody asexual or sexual
stem

Coniferophyta Yes Yes Yes, woody Yes Seed, sexual

stem reproduction.
Angiospermophyta Yes Yes Yes, woody Yes Seeds, Sexual
stem reproduction.

Leaves
- Any usually flattened green outgrowth from the stem.
Roots
- The part of a plant which attaches it to the ground or to a support, typically
underground, conveying water and nourishment to the rest of the plant via numerous
branches and fibers.
- Rhizoids do not absorb water or nutrients from the substrate; instead, their main
function is to attach the plant to its substrate.
Stems
- the plant axis that bears buds and shoots with leaves and, at its basal end, roots.

Vascular tissue
- the tissue that constitutes the vascular system, consisting of phloem and xylem. by
which water and nutrients are conducted throughout the plant.

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1.5 Dichotomous key
- used as a guiding list whether there are characteristics in the unknown species the
same as the known species.
- a tool that can be used to identify organisms or objects in the natural world
- consists of a series of paired statements or clues about features or characteristics
providing a stepwise guide toward identifying each entity.
- useful for biological classification and identification

● Vertebrate classes (Tree diagram)

○ has fur / no fur
■ no fur: No feathers / Feathers
● No feathers: external fertilization / internal fertilization
○ external fertilization: gills in adult / no gills in adult

- number of classing: n-1

How to construct a dichotomous key

- have a close observation of the given picture to identify the species
-