Animal Kingdom

Question 1

Phylum

Answer 1

• Highest unit of classification after ‘Kingdom’
• Animals grouped into phyla based on shared characteristics
• Animals are heterotrophs, with no cell wall

Question 2

Nematodes

Answer 2

• Round worms
• Many species, around 25,000 described
• Most abundant animals in Antarctica
• Moult (like arthropods)
• Eutelic (fixed number of cells/species)

Question 3

Tardigrades (‘Water bears’ or ‘Moss Piglets’)

Answer 3

• Live in fresh water, moss and undergrowth
• Capable of surviving extremes (10 years without water)
• On final flight of space shuttle Endeavor
• Also eutelic (species specific number of cells)

Question 4

Eutelic

Answer 4

Eutelic organisms have a fixed number of somatic cells when they reach maturity, the exact number being constant for any species

Development proceeds by cell division until maturity; further growth occurs via cell enlargement only.

Question 5

Phylum: Onychophora

Answer 5

• Velvet worms or Claw bearers
• Terrestrial
• Have antennae (unique for worms)
• Capture prey by throwing out sticky threads

Question 6

Eumetozoa

Answer 6

• Subkingdom
• Eumetozoa divided into:
• radially symmetrical animals e.g. cnidiaria, ctenophora
• bilaterally symmetrical animals e.g. bilateria
• Bilateria divided into:
• protostomes e.g. flatworms, segemented worms, molluscs, arthropods
• deterostomes e.g. echinoderms, chordates

Question 7

Symmetry

Answer 7

• Bilateral Symmetry
• have one plane along which they are symmetrical
• can talk about anterior/posterior, dorsal/ventral, left/right
• Radial symmetry
• have several planes along which they are symmetrical

Question 8

Germ layers

Answer 8

• later of embryonic cells that develops into body features
• ecto, meso, endo
• Diploblastic = two layers, no mesoderm, no gut cavity
• Tripoblastic = three layers

Question 9

Blastula

Answer 9

• blastula = early developmental stage when cells begin to differentiate
• morula = ball of cells

Question 10

Tripoblast

Answer 10

• 3 germ layers
• if the organism has a gut, must be a triploblast but a triploblast may not have a gut
• acoelomate = coelom absent
• coelomate = coelom present

Question 11

The importance of the coelom

Answer 11

1. • Fluid-filled so can be used as internal support
2. • separates internal processes from gut
3. • allows transport of fluids (circulatory and excretory systems)
4. • provides space for development of internal organs
5. • enables increased body size

Question 12

Fate of the Blastopore

Answer 12

• Protostome = ‘mouth first’
• blastopore becomes the mouth
• spiral cleavage, determinate development
• Deuterostome = ‘anus first’
• blastopore becomes the anus
• echinoderms and chordates
  e. g. in humans, needs to get rid of wastes first in the uterus, does not eat via the mouth but gets nutrients via the umbilical cord

Question 13

Segmentation

Answer 13

• Segmentation affects mesoderm and ectoderm
• series of repetitive segments
• Advantages: efficient movement, detect prey (mouth, head, sensory organs), specialisation, better adaptation (allow body organ to grow differentially, suited for a specific purpose)

Question 14

Other important ways of distinguishing animals

Answer 14

• Moulting - Ecdysozoa (arthropods)
• Feeding mechanisms
• Larval biology - trophocore larvae (e.g. annelids, molluscs)
• Reproduction - sexual/asexual (most species sexaul; some asexual; some sexual and asexual)

Question 15

Subgkindom: Parazoa

Phylum: Porifera - Sponges

Answer 15

• Simplest animals
• Aquatic, mainly marine
• No mouth or gut
• Layers of cells with protein matrix; no tissues or organs
• No nervous system
• Mainly filter feeds
• Have specialised cells - pinoctyes - can engulf larger prey
• Sexual and asexual reproduction

Question 16

Subkingdom: Eumetozoa

Phylum: Cnidaria

Answer 16

• Split into three classes

1. Hydras (Hydrazoa)
2. Jellyfish (Scyphozoa)
3. Corals and Anemones (Anthozoa)

• Radia symmetry (mostly)
• Diploblastic: two body layers are separated by a gelatinous layer called the mesoglea
• Aceolomate
• Unsegmented
• Nerve net, in the mesoglea, simple nervous system
• Reproduction - usually sexual and asexual
• Use nematocysts to catch prey, barbed wire within specialised cell, cnidoctye

Question 17

Typical Cnidarian life cycle

Answer 17

• asexual polyp stage
• sexual medusae stage
• Medusa, free to swim, Jellyfiish
• Sessile, fixed onto ocean floor

Reproduction begins when the females catch sperm released by the males to fertilize the eggs she has produced and holds it in her mouth. These fertilized eggs remain attached to her oral arms, and there they grow into flat bean-shaped planula. Once they grow into flower-shaped polyps, they are released into the ocean where they attach themselves to a solid surface and undergo budding.

Polyps reproduce asexually, producing medusae that then release gametes. The male and female gametes unite under water to form the zygote that then develops into larva and later produces another polyp.

The form that reproduces asexually is the polyp. Polyps produce medusae via budding in Obelia and via strobilation in Aurelia.

Question 18

Phylum: Cnidaria

Class: Hydrozoa (Hydra)

Answer 18

• Freshwater polyp
• Long tentacles for prey capture with stinging nettles
• Anchored by ‘foot’

Question 19

Phylum: Cnidaria

Class: Schyphozoa (Jellyfish)

Answer 19

• Marine, free-swimming
• Also have stinging tentacles (sometimes enormously poisonous)
• One of the world’s longest animals is the lion’s mane jellyfish (200ft long)

Question 20

Phylum: Cnidaria

Class: Anthozoa (Corals and anemones)

Answer 20

• marine polyps
• often colonial
• many have symbiotic algae living intra-cellularly, coral provies algae with nutrients and protection, algae provides coral with N₂ and organic C compounds

Question 21

Subkingdom: Eumetozoa

Phylym: Platyhelminthes

Answer 21

• Flatworms
• two modes of living: free-living or parasitic
• four classes:

1. Turberllaria: aquatic flatworm, free-living
2. Monogenea: external flukes, parasitic
3. Trematoda: internal flukes, parasitic
4. Cestoda: tapeworms, parasitic

• bilateral
• triploblastic
• acoelomate
• protostome - simple gut with mouth only
• unsegmented
• bottom surface may be covered in cilia - aids movement

eye > brain > ventral nerve cord > pharynx > mouth/anus

Question 22

Tapeworms

Answer 22

• vertebrate gut parasites
• attach to intestinal lining via head structure (scolex)
• feed by absorption through epidermis (very thin/flat)
• reproduce by breaking off body segments (proglottids)
• can grow very long…3 metres plus
• famously used as a diet aid