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Title: Classification notes
Description: Notes include all important definitions needed for Biology A level, as well as an overview of the Kingdoms and their Phyla, with special focus on the Animal Kingdom.
Description: Notes include all important definitions needed for Biology A level, as well as an overview of the Kingdoms and their Phyla, with special focus on the Animal Kingdom.
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CLASSIFICATION
Biodiversity - variety of life in all its forms, levels and combinations
...
Threats to Ecosystem diversity:
Climate Change, Habitat Destruction, Invasion of alien species, Pollution, acid rain, deforestation,
oil spills, eutrophication, illegal fishing, overhunting, pesticides, earthquakes, volcanic eruptions,
wildfires, tornadoes, pathogens (viruses), dredging (digging canals in sea beds)
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Example - when horse and donkey mate they produce a mule - sterile - therefore they
are two different species
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Science of classification - Taxonomy: Nomenclature - naming of organisms using genus + species
name (Binomial system) e
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Homo sapiens; Systematics - placing of organisms into groups on the
basis of similarities and differences
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E
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Classification of man: Animalia, Chordata, Mammalia, Primates, Hominidae, Homo, sapiens
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g
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In nature male has to convince female to copulate :
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Classifying organisms:
Artificial vs Natural Classification —> Artificial classification - based on one/few easily observed
characteristics; Natural classification - uses natural relationships between organisms
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Considers similarities in embryology, morphology, anatomy, physiology,
biochemistry, cell structure & behaviour
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Phylogenetic Classification —> based on evolutionary relationships - organisms in the same
group are believed to have a common ancestor - can be shown by a phylogenetic tree (bacteria at
bottom - branch into different kingdoms)
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It
is a homologous structure because it is structurally the same in tetrapods (4 limbs)
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Closely related organisms will have an
embryo that is similar in appearance e
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mammalian embryos are quite similar at an early stage
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In protostomes the blastopore becomes
their mouth e
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insects, molluscs
...
g
...
Biochemistry —> organisms make use of a protein known as cytochrome ‘c’ which transfers
electrons within the mitochondrion and energy is formed
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The amino acids
making up this protein in men and in chimps are identical
...
E
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hydra, starfish, octopus, jellyfish
...
E
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Humans
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E
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Hydra
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E
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Humans
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Mesoderm of the adult completely fills the region between the
ectoderm and the endoderm
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g
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Pseudocoelomate —> Mesoderm is confined to specific, circumscribed regions so that there is an
extensive body cavity between the body wall and the alimentary system
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g
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Coelomate —> Triploblastic
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Free space enclosed by the peritoneum - coelom
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g
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Metameric Segmentation —> In annelids, arthropods and vertebrates
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Advantages: Repetition of a pattern is useful on the principle that there is safety in
numbers + once a repeat pattern is available the units of pattern can become elaborated and
specialised in various ways
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Transition of gills to lungs —> Allowed organisms to exploit the terrestrial environment
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Most
amphibians start off life as gill-breathing e
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tadpole fish-like larvae and then they undergo
numerous changes to produce lung-breathing adults
...
Cleidoic egg —> An egg that is enclosed by a shell which effectively isolates it from the outside
environment and prevents the loss of moisture e
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the egg of a land-dwelling animal
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Piece of DNA encapsulated in a protein coat
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Enigmatic - start reproducing when faced with the right conditions (temp
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Smallest organisms - borderline of living/non-living
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Pathogens - cause diseases
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Bacteriophage - a virus which attacks bacteria - injects DNA into bacteria, viral DNA makes
bacteria produce proteins
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g
...
The virus fits tail fibres into specific proteins on the
host cell
...
The base plate releases an enzyme known as
lysozyme which helps penetrate the membrane
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The DNA passes down the hollow spike into the
host cell
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The viral SNA makes use of the bacterial/host
ribosomes, to produce enzymes that destroy the
bacterial/host DNA
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The viral DNA replicates
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The ribosomes are used to make viral protein for
the virus
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Lysogenic Viruses - Attach to the DNA of the host
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Lytic Viruses - Viruses which once they enter the body, symptoms show up soon after
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E
...
Flu viruses
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Bacteria
-
Kingdom Monera/Prokaryotae
No Post-transcriptional processing in Bacteria - translated there and then - no introns/exons
Bacteria form Endospores
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Asexual —> DNA replicates
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Many bacteria are beneficial:
• production of yoghurt - lactobacillus used to convert lactose into lactic acid (makes yoghurt turn
sour)
...
- fix Nitrogen in the form of Ammonium, then Nitrite, then
Nitrate
...
g
...
• Production of insulin
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• Cheese production
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• Farmers - use hay - semi-ferment it with bacteria
(semi solid jelly like) slurry —> beneficial for
animals
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Preventing waste
from secreting harmful, toxic substances
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• Sexual reproduction
Above step happens by direct physical contact between recipient & donor
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Circular strand of DNA which is separate from the normal bacterial chromosomes
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• During Conjugation the F+ cell initiates the elongation of the F Pillus (tube like structure made of
protein) serves as tunnel to transfer DNA (bridges cells together)
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• Genetic information transferred is beneficial e
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antibiotic resistance
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• Sexual —> 2 producing 1 new organism, partner is necessary, if isolated cannot procreate
sexually, may go extinct, genetic variation
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Recipient discards a piece of DNA - replaced with a homologous piece of DNA from donor
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Donor releases DNA in immediate environment of recipient
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Must express appropriate enzymes for plasmid of DNA to be taken up in immediate environment
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• Bacteriophage lands on bacterium and takes up DNA, then infects another bacterium with viral +
bacterial DNA
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Protoctista
- Either animal like - amoeba & paramecium; or plant like - euglena, chlorella, chlamydomonas
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- Algae are plant-like, photosynthetic and mainly aquatic
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g
...
, Spirogyra, Chlamydomonas ; Phaeophyta (brown algae) e
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Fucus sp
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- Protozoa are animal-like, unicellular and mainly aquatic
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g
...
g
...
g
...
g
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- Fungus-like are split into Phylum: Oomycota e
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Phytophora infestans (potato blight)
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Fungi
-
Eukaryotes
Lack chlorophyll —> heterotrophic nutrition
Made up of hyphae (apically elongated walled filaments)
Cell wall present made of chitin
Reproduce by spores
3 phyla - Zygomycota, Ascomycota, Basidiomycota
...
g
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Asexual reproduction by sporangia containing sporangiospores
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Saprophytes - extracellular
digestion
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g
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- Basidiomycota - E
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Agaricus campestris (field mushroom)
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Animalia
- Eukaryotic, no cell walls, multicellular, Heterotrophic nutrition (ingestion & egestion)
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- Jointed appendages - greater flexibility in movement
...
- Presence of a notochord which is a flexible rod that develops long the back of the embryo;
muscles attach attach to the outside of this rod; gave rise to the vertebrates (the notochord
stiffness and becomes bony and changes into the vertebral column of vertebrates)
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Cnidaria/Coelenterata
- Simplest animal
...
g
...
3 classes: Hydrozoa, Scyphozoa,
Anthozoa
...
The ectoderm and endoderm are separated by a structureless gelatinous layer mesoglea
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- Mouth leads to a single gastrovascular cavity, in which digestion, gas exchange, gas exchange
-
and circulation take place
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For dispersal and reproduction
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Umbrella shaped)
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Flame cells - excretion
Class Hydrozoa —> Hydra, Obelia - dominant polyp stage
Class Scyphozoa —> Aurelia (jellyfish) - dominant medusa stage (marine)
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Platyhelminthes
Flatworms - bilateral symmetry
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Triploblastic, Acoelomate (only group), Cephalisation
Unsegmented, Mouth present but anus absent
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Dorso-ventral flattening - thin body - flat
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g
...
- Class Trematoda —> E
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Fasciola (liver fluke), parasite, hermaphrodite, body covered in spine
for protection and to penetrate wall of the bile duct
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g
...
- Tapeworm life-cycle: When proglottids are mature enough they become detached from the
main body and are passed out with the faeces
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Only if these resistant eggs are swallowed by a
pig does development proceed
...
This hollow sphere of cells has 6
hooks and is known as an onchosphere
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The embryo
settles in various parts of the host e
...
the muscle tissue where it loses its hooks and increase
in size
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This is the blasserworm or cystercus stage (invaginated
scolex)
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Howver, if
eaten in an ‘underdone’ state then the worm, which can survive a considerable amount of
hear, will finish its life cycle
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The bladder portion is digested and the scolex attached itself to the intestinal
wall, where it commences to bud off new proglottids
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Bilateral symmetry, Triploblastic, Coelomates, Metameric Segmentation, Cephalisation
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Well developed excretory & circulatory systems
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- Prostomium - lip-like extension of the 1st segment situated above the mouth
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Provides support, protection and locomotion
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g
...
-
- Class Oligochaeta —> E
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earthworm - lack of cephalisation (no distinct head), few chaetae, No
parapodia, nocturnal (only come out at night), Hermaphrodite - cross-fertilisation via clitellum,
Direct life cycle, no eyes, Detrivore (feeds on dead vegetation and matter), maintain sold
structure and fertility, aerate soil - improving drainage and allowing oxygen to reach plant roots
...
- Class Hirudinea —> E
...
leech - no distinct head, no parapodia, clitellum present, ectoparasite,
3 chitinous teeth in a Y-shape, used in medicinal practice since they remove any blood clots and
help in cleaning the wound
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Bilateral symmetry, Triploblastic, Coelomates, Metameric segmentation, mouth & anus present
Jointed appendages present, exoskeleton made of chitin/calcareous matter
...
- Class Insecta —> Mostly terrestrial, have 3 segments - head, thorax and abdomen, pair of
simple & compound eyes, pair of antennae, internal fertilisation, 3 pairs of legs attached with 1
or 2 pairs of wings, Dioecious (male + female),undergo complete & incomplete metamorphosis,
important for the environment & ecosystem - production of honey and silk and as decomposers
...
- Class Arachnida —> terrestrial, simple eyes, no larval form present, no antennae, no ‘true’
mouthparts, 4 pairs of legs present, cephalothorax present, respiration through lung books
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- Snails, oysters, slugs, clams, octopuses and squids
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- Class Gastropoda —> E
...
Helix aspersa (land snail) - asymmetrical, anus is anterior, large flat
foot present - used for locomotion which contains a slime gland that secretes a film of mucus
over which the snail moves by means of wavelike contractions of the muscular foot, Visceral
mass is contained in a spirally coiled shell due to rotation of hump during growth (torsion - anus
near mouth), distinct head with eyes & sensory tentacles, presence of radula - rasping tonguelike structure used for feeding, internal fertilisation, hermaphrodite, cross fertilisation, land forms
lost gills and converted mantle cavity into a lung
...
g
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- Class Cephalopoda —> E
...
Octopus vulgaris (octopus) - aquatic, bilateral symmetry, no torsion
of visceral mass, shell often reduced and internal or absent (octopus), head highly developed,
tentacles with numerous suckers present, well developed eyes, anus is posterior, internal
fertilisation, gills are present, adapted for fast swimming, food modified to form part of the head
and the tentacles, radula/horny beak present, carnivorous predators, able to inject a poison from
the mouth into the organism to paralyse it, ink sac near anus to distract predators, have highly
developed nervous systems, exhibit complex patterns of behaviour and a high level of
intelligence
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- Class Asteroidea —> e
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Asterias (starfish), star shaped, flattened, radial symmetry pentamerous symmetry (5 arms), external fertilisation, movable spines guarding the ambulacral
groove (leads to mouth), separate sexes, body covered by a flexible but tough integument,
underneath which one finds a number of calcareous plates —> dermal skeleton, carnivore,
pedicellariae - pincer-like structures which keep the surface of the animal clean (found around
base of spines), Dermal spores - found in between spines, fine gills project from them which can
be pulled in if organism is being attacked, Madreporite - on upper surface bears external
openings to water vascular system, food is partly digested outside the body because the
stomach can evert - vomit and re-digest, larva can locomote, 2 types of tube feet - light sensitive
feet (detect light) + tube feet in ambulacral groove which end in suckers (used for locomotion
and feeding) - can be attacked by predators - if so starfish dies
...
g
...
Chordata
- Presence of a notochord, dorsal tubular nerve cord, pharyngeal gill slits (in embryonic form,
though they persist in some), a post-anal tail (persists but some lose it in embryonic form)
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- Nerve cord —> single, dorsal, anterior end enlarged to form brain; IMP - success in
chordates; development of complex systems for sensory perception, integration + motor
responses; runs along longitudinal axis, dorsal to notochord
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In some chordates have become gill pouches (gills never break to outside); filter
feeding; gills - gas exchange; gill slits - embryonic
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- Triploblastic, Coelomates, Bilateral symmetry, notochord present, internal skeleton present, well
developed nervous system (including the brain), closed circulatory system present, 2 pairs of
limbs present
...
g
...
- Class Amphibia —> E
...
Discoglossus Picus (Maltese Painted Frog), Poikilothermic, Production
of eggs, 2 pentadactyl limbs present (hind limbs with 5 digits, long for swimming/ front limbs
short with 4 digits, act as support and as a shock absorber from jumps), tympanic membrane
covering middle ear opening, metamorphosis occurs, no scales, 3rd eyelid present for
swimming, nostrils and teeth present
...
g
...
- Class Aves —> E
...
Columbidae (Pigeons) - Homeothermic - Warm Blooded, Production of
calcareous eggs, high metallic rate, internal fertilisation, no external ear present, feathers and
scales present, toothless jaws, 3rd eyelid present for flight protection, 2 pairs of pentadactyl
limbs for grasping, walking and flying, 2 types of feathers (long quill feathers of tail, small covert
feathers trap air and are needed for water and heat insulation)
...
g
...
- Oviparous (egg laying) - Monotremes are mammals in which eggs are internally fertilised and
then are laid and embryo hatches out of the egg
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g
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Still suckle young
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Eggs are very small and are
fertilised internally
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Young are born at an advanced stage of development and are
then fed from milk produced by the mother’s mammary glands
...
They thus crawl into an abdominal pouch called the marsupium where they continue their
development, nourished by the mother’s milk e
...
kangaroos, koalas
Title: Classification notes
Description: Notes include all important definitions needed for Biology A level, as well as an overview of the Kingdoms and their Phyla, with special focus on the Animal Kingdom.
Description: Notes include all important definitions needed for Biology A level, as well as an overview of the Kingdoms and their Phyla, with special focus on the Animal Kingdom.