Intro to
Kingdom
Animalia
aka us and a bunch of other
stuff
First off…
• What is an animal?
• MAIN IDEA: An animal is a multicellular eukaryotic heterotroph
whose cells lack cell walls
• Plant + Fungi have cell walls, where animals don’t
• Multicellular means division of labour with specialised cells
Surviving as an Animal
Every animal has to do these things in some way
• Feeding
• Respiration
• Internal Transport (movement of nutrients etc throughout body)
• Excretion
• Response (to a bunch of stimuli)
• Movement (although some are sessile)
• Reproduction (mostly sexual, some asexual forms)
Body forms and structure
• 2 forms of animal, vertebrate (backbone) and invertebrate (no
backbone). Vast majority are invertebrate
• 3 types of skeleton structure exist:
1: Hydrostatic Skeleton
• No hard structures, muscles surrounded and supported by
water-filled body cavity – Cnidarians and some worms for
example
Forms cont.
2: Exoskeleton
• Hard outer layer (exo = outer)
• Rigid frame to support bodyweight
• Protects internal tissue/organs from predation
• Usually water-impermeable (prevents water loss)
• Ex. arthropods, some shelled mollusks, crustaceans
3: Endoskeleton
• Interior framework (endo = inner)
• Muscle attaches to outer surface of endoskeleton
• Allows for larger bodies
• More flexible
• Ex. vertebrates (like us), sponges, and echinoderms
Skeletons are made of different
materials such as:
• Calcium carbonate (corals, sea
urchin)
• Chitin (arthropods and some
crustaceans)
• Silica (some sponges)
• Cartilage (cartilaginous sharks)
• Bones (vertebrates like us)
Reproduction in Animals
Can be Asexual or Sexual
Asexual
• Fragmentation and budding
• Rapid production of offspring from a single individual
• Does not provide genetic diversity
• Not as common among animals, mostly seen in
sponges and cnidarians, and some worms
Sexual Reproduction
• Large majority of animals undergo sexual reproduction (especially as
they become more complex)
• Most have separate sexes (male + female) but some are
Hermaphroditic (produce sperm and eggs) and can fertilise each
other
• Forms new genetic combinations which may make offspring more
successful
• Overall slower reproduction time
• Fertilisation can be external (like salmon) or internal (most mammals)
Early Development of Animals
• After fertilisation, a zygote is formed (sperm + egg)
• Zygote divides and becomes an embryo, keeps dividing multiple
times until it has 8-cells
• At this point, it can follow Spiral or Radial cleavage patterns
• Spiral is associated with Protostomes
• Radial is associated with Deuterostomes
Both of these patterns continue dividing until forming a hollow
ball called the Blastula
Protostomes and deuterostomes can be separated by their early
cleavage patterns, development, and what end the blastospore
forms
• Determinate development = cells have specific fates early on, so
if they die the rest of the cells are altered/development halts
• Indeterminate development = all cells can become anything so
the loss of one cell does not stop development
• Blastopore = folded-in hole formed in the blastula
Protostome
• Spiral cleavage
• Determinate development
• Blastopore becomes mouth
Deuterostome
• Radial cleavage
• Indeterminate development
• Blastopore becomes anus
The Germ Layers
• Animals have 3 germ layers, all continue to divide
Ectoderm: layer of cells on the outside of the blastula,
eventually forms epithelial and neural tissues (skin, hair, spinal
cord, brain)
Endoderm: layer of cells folded inside the blastula ( inner
layer), eventually forms inner lining of digestive and respiratory
tract
Mesoderm: middle layer between the other two, slightly
different between the ‘stomes, forms muscles and body cavity