Animal Kingdom, Morphology & Classification

• Classification is arranging organisms into groups and sub-groups by shared features.
• Taxonomy is the science of naming, describing and grouping organisms.
• Systematics studies kinds of organisms and the relationships among them.
• Classification makes study easy, shows relationships, and reveals the path of evolution.
• The descending order of taxa is Kingdom > Phylum > Class > Order > Family > Genus > Species.
• Species is the basic (lowest) unit of classification.

Classification is arranging organisms into groups and sub-groups by shared features.

Taxonomy is the science of naming, describing and grouping organisms.

Systematics studies kinds of organisms and the relationships among them.

Classification makes study easy, shows relationships, and reveals the path of evolution.

Species is the basic (lowest) unit of classification.

• Aristotle made the first scientific classification using morphological characters; called the Father of Biology.
• Linnaeus introduced binomial nomenclature – a twoword Latin name (Genus + species), e.g. Homo sapiens; he is the Father of Taxonomy.
• R. H. Whittaker (1969) proposed the modern Five Kingdom classification.
• Two-kingdom system failed because it mixed prokaryotes with eukaryotes and plants with fungi.
• Aristotle — Father of Biology; first classification
• Linnaeus — Two Kingdoms; binomial naming; Father of Taxonomy
• Whittaker — Five Kingdom system (1969)
• Carolus Linnaeus gave the Two Kingdom system: Plantae and Animalia.

Aristotle made the first scientific classification using morphological characters; called the Father of Biology.

Linnaeus introduced binomial nomenclature – a twoword Latin name (Genus + species), e.g. Homo sapiens; he is the Father of Taxonomy.

R. H. Whittaker (1969) proposed the modern Five Kingdom classification.

Two-kingdom system failed because it mixed prokaryotes with eukaryotes and plants with fungi.

Carolus Linnaeus gave the Two Kingdom system: Plantae and Animalia.

• Whittaker's criteria: cell structure, body organisation, nutrition, reproduction and evolutionary relationships.
• Monera are prokaryotes (bacteria); Protista are unicellular eukaryotes.
• Fungi are heterotrophic with a chitin cell wall.
• Plantae are autotrophic with a cellulose cell wall.
• Animalia cells have no cell wall, so they stay soft and flexible.
• Monera — Prokaryote — Wall present
• Protista — Eukaryote, unicellular — Mixed nutrition
• Fungi — Eukaryote — Chitin wall, heterotroph
• Plantae — Eukaryote — Cellulose wall, autotroph
• Animalia — Eukaryote — No wall, heterotroph

Monera are prokaryotes (bacteria); Protista are unicellular eukaryotes.

Fungi are heterotrophic with a chitin cell wall.

Plantae are autotrophic with a cellulose cell wall.

Animalia cells have no cell wall, so they stay soft and flexible.

• Mycoplasma (PPLO) is the smallest organism capable of autonomous growth and reproduction.
• Mycoplasma has no cell wall and is the smallest known living cell.
• Viruses are smaller still but are non-living outside a host (need a host to reproduce).
• Order of size: bacteria > Mycoplasma/PPLO > virus.
• Bacteria are the smallest true cellular (prokaryotic) organisms.

Mycoplasma (PPLO) is the smallest organism capable of autonomous growth and reproduction.

Mycoplasma has no cell wall and is the smallest known living cell.

Viruses are smaller still but are non-living outside a host (need a host to reproduce).

Bacteria are the smallest true cellular (prokaryotic) organisms.

• All animals are multicellular eukaryotes with no cell wall.
• Animals are heterotrophic – they eat other organisms as they cannot photosynthesise.
• Stored food is mainly glycogen or fat.
• Most animals show locomotion and reproduce sexually.
• By the backbone, animals split into Invertebrates (no backbone) and Vertebrates (with backbone).

All animals are multicellular eukaryotes with no cell wall.

Animals are heterotrophic – they eat other organisms as they cannot photosynthesise.

Stored food is mainly glycogen or fat.

Most animals show locomotion and reproduce sexually.

By the backbone, animals split into Invertebrates (no backbone) and Vertebrates (with backbone).

• Cellular level – loose cells with little division of labour, as in sponges (Porifera).
• Tissue level – similar cells form tissues, as in coelenterates (Cnidaria).
• Organ level – tissues form organs, as in Platyhelminthes (flatworms).
• Organ-system level – organs work as systems, as in annelids, arthropods, molluscs and chordates.
• Complexity rises in this order, showing an evolutionary trend.
• Cellular — Porifera (sponges)
• Tissue — Cnidaria (coelenterates)
• Organ — Platyhelminthes
• Organ-system — Annelids, arthropods, chordates

Cellular level – loose cells with little division of labour, as in sponges (Porifera).

Tissue level – similar cells form tissues, as in coelenterates (Cnidaria).

Organ level – tissues form organs, as in Platyhelminthes (flatworms).

Organ-system level – organs work as systems, as in annelids, arthropods, molluscs and chordates.

Complexity rises in this order, showing an evolutionary trend.

• Asymmetrical – no plane gives equal halves, as in sponges.
• Radial symmetry – any plane through the central axis gives two identical halves.
• Radial symmetry occurs in Coelenterata, Ctenophora and adult Echinodermata.
• Bilateral symmetry – only one plane gives matching left and right halves.
• Bilateral symmetry occurs in annelids, arthropods and chordates and is more advanced.
• Asymmetrical — Sponges
• Radial — Coelenterata, Echinodermata
• Bilateral — Annelids, arthropods, chordates

Asymmetrical – no plane gives equal halves, as in sponges.

Radial symmetry – any plane through the central axis gives two identical halves.

Bilateral symmetry – only one plane gives matching left and right halves.

Bilateral symmetry occurs in annelids, arthropods and chordates and is more advanced.

• Embryos are built from cell sheets called germ layers.
• The outer layer is ectoderm; the inner layer is endoderm.
• Diploblastic animals have two layers (ectoderm + endoderm), e.g. coelenterates.
• Triploblastic animals have a middle mesoderm as well, from flatworms up to chordates.
• Mesoderm forms muscles, skeleton, heart and internal organs, allowing complex bodies.
• Diploblastic — Ecto + Endoderm — Coelenterates
• Triploblastic — Ecto + Meso + Endoderm — Flatworms to chordates

Embryos are built from cell sheets called germ layers.

The outer layer is ectoderm; the inner layer is endoderm.

Diploblastic animals have two layers (ectoderm + endoderm), e.g. coelenterates.

Triploblastic animals have a middle mesoderm as well, from flatworms up to chordates.

Mesoderm forms muscles, skeleton, heart and internal organs, allowing complex bodies.

• A coelom is a fluid-filled space between the body wall and the gut.
• Coelomates have a true coelom lined by mesoderm – annelids, molluscs, arthropods, echinoderms, chordates.
• Pseudocoelomates have a false cavity not lined by mesoderm, e.g. Aschelminthes (roundworms).
• Acoelomates have no body cavity, e.g. Platyhelminthes (flatworms).
• The cavity gives room for organs to grow, fold and move, so it is a key classification clue.
• Coelomate — True, mesoderm-lined — Annelids, chordates
• Pseudocoelomate — False cavity — Roundworms
• Acoelomate — Absent — Flatworms

A coelom is a fluid-filled space between the body wall and the gut.

Coelomates have a true coelom lined by mesoderm – annelids, molluscs, arthropods, echinoderms, chordates.

Pseudocoelomates have a false cavity not lined by mesoderm, e.g. Aschelminthes (roundworms).

Acoelomates have no body cavity, e.g. Platyhelminthes (flatworms).

• Porifera – sponges; pores and cellular level; asymmetrical.
• Coelenterata (Cnidaria) – Hydra, jellyfish, corals; tissue level; diploblastic.
• Platyhelminthes – flatworms, tapeworm, liver fluke; flat, acoelomate.
• Aschelminthes – roundworms (Ascaris); pseudocoelomate.
• Annelida – earthworm, leech; segmented body; true coelom.
• Arthropoda – insects, crabs; largest phylum; jointed legs and chitin exoskeleton.
• Mollusca – snail, octopus; soft body, often shelled; Echinodermata – starfish, spiny skin.

Porifera – sponges; pores and cellular level; asymmetrical.

Coelenterata (Cnidaria) – Hydra, jellyfish, corals; tissue level; diploblastic.

Platyhelminthes – flatworms, tapeworm, liver fluke; flat, acoelomate.

Aschelminthes – roundworms (Ascaris); pseudocoelomate.

Annelida – earthworm, leech; segmented body; true coelom.

Arthropoda – insects, crabs; largest phylum; jointed legs and chitin exoskeleton.

Mollusca – snail, octopus; soft body, often shelled; Echinodermata – starfish, spiny skin.

• Pisces (fish) – gills, fins, cold-blooded, scales.
• Amphibia – frogs, toads; live on land and water; moist skin.
• Reptilia – snakes, lizards, turtles; dry scaly skin; lay eggs on land.
• Aves (birds) – feathers, wings, beak; warm-blooded; lay eggs.
• Mammalia – hair, mammary glands; warm-blooded; mostly give birth to young.
• Pisces — Gills, fins, scales
• Amphibia — Moist skin, dual life
• Reptilia — Dry scaly skin
• Aves — Feathers, beak
• Mammalia — Hair, mammary glands

Pisces (fish) – gills, fins, cold-blooded, scales.

Amphibia – frogs, toads; live on land and water; moist skin.

Reptilia – snakes, lizards, turtles; dry scaly skin; lay eggs on land.

Aves (birds) – feathers, wings, beak; warm-blooded; lay eggs.

Mammalia – hair, mammary glands; warm-blooded; mostly give birth to young.

• Most mammals give birth to live young, but the egglaying mammals (monotremes) are exceptions.
• The Platypus (duck-billed platypus) and the Echidna (spiny anteater) lay eggs yet feed milk.
• Whales and dolphins are mammals, not fish – they breathe air with lungs.
• The Sperm whale is the largest of the toothed whales.
• The Blue whale is the largest animal ever to have lived.

Most mammals give birth to live young, but the egglaying mammals (monotremes) are exceptions.

The Platypus (duck-billed platypus) and the Echidna (spiny anteater) lay eggs yet feed milk.

Whales and dolphins are mammals, not fish – they breathe air with lungs.

The Sperm whale is the largest of the toothed whales.

The Blue whale is the largest animal ever to have lived.

• Apes (gibbon, orangutan, gorilla, chimpanzee) have no tail, unlike monkeys.
• The Gibbon is the smallest man-like ape.
• The Gorilla is the largest living ape.
• Humans belong to the order Primates, scientific name Homo sapiens.
• Chimpanzee is the ape genetically closest to humans.

Apes (gibbon, orangutan, gorilla, chimpanzee) have no tail, unlike monkeys.

The Gibbon is the smallest man-like ape.

The Gorilla is the largest living ape.

Humans belong to the order Primates, scientific name Homo sapiens.

• Honey and beeswax come from the honeybee.
• Silk comes from the silkworm (Bombyx mori).
• Lac (shellac) comes from the lac insect.
• Cochineal dye is obtained from the cochineal insect.
• Pearls are NOT from insects – they come from oysters (molluscs); a common trick option.
• Honey, wax — Honeybee
• Silk — Silkworm
• Lac — Lac insect
• Cochineal dye — Cochineal insect
• Pearl (not insect) — Oyster (mollusc)

Honey and beeswax come from the honeybee.

Silk comes from the silkworm (Bombyx mori).

Lac (shellac) comes from the lac insect.

Cochineal dye is obtained from the cochineal insect.

Pearls are NOT from insects – they come from oysters (molluscs); a common trick option.

• Female Anopheles spreads malaria and sits with its body tilted, at an angle to the surface.
• Female Culex rests with its body parallel to the surface and spreads filaria.
• Female Aedes spreads dengue, chikungunya and yellow fever.
• Only female mosquitoes bite, as they need blood to develop eggs.
• Aedes has a black-and-white striped body and bites mostly by day.
• Anopheles — Malaria
• Culex — Filaria
• Aedes — Dengue, yellow fever

Female Anopheles spreads malaria and sits with its body tilted, at an angle to the surface.

Female Culex rests with its body parallel to the surface and spreads filaria.

Female Aedes spreads dengue, chikungunya and yellow fever.

Only female mosquitoes bite, as they need blood to develop eggs.

• The camel can live the longest without drinking water and is the ship of the desert.
• The kangaroo rat can survive almost entirely on metabolic water from food.
• Camels store fat (not water) in the hump for energy.
• Warm-blooded (homeothermic) animals keep a steady body temperature; cold-blooded ones change with surroundings.
• Desert animals reduce water loss through concentrated urine and dry dung.

The camel can live the longest without drinking water and is the ship of the desert.

The kangaroo rat can survive almost entirely on metabolic water from food.

Camels store fat (not water) in the hump for energy.

Warm-blooded (homeothermic) animals keep a steady body temperature; cold-blooded ones change with surroundings.