Kingdom animalia

What features do animals have that separate them from plants and fungi?

No cell walls

Possess a gut (enteron) which digesrion takes place

Nervous system

Can move

Body structure of cnidarians

Radically symmetrical - can respond to its environment through 360 degrees (can catch prey in any direction)

Gut cavity (enteron) is sac like with only one entrance, a mouth - food digested and undigested food egested

Tentacles contain cnidcystes - stinging cells used to catch food, conveyed by tentacles to the mouth

Body supported by surrounding aqueous medium and hydrostatic skeleton formed by fluid- filled enteron

Movement is limited - jellyfish movement dictated by ocean currents, hydra is often sedentary but can undertake cartwheel movements

How do Platyhelminthes differ from cnidarians?

Bilateral symmetry while cnidarians are radically symmectrical

Flatworms include free-living __________ and parasitic ___________ and ______________.

Planarians, flukes, tapeworms

Features of a planarian body - body

- bilaterally symmetrical so body can move forward in search for food ~ movement in one direction means that front end (head with sensory organs - eyes, likely site for a mouth) evolves as well as a specialised ventral surface with a distinct dorsal surface.

- dorso-ventrally flattened so large SA-V ratio

- body supported by aqueous medium, well packed cells in body provide a supportive role

- soft body = no specialised skeletal system

Features of planarian body- gut

Only has single opening and highly branched- permeating all parts of the body

Result of branched gut and flattened shape- no cell in the body is far from either gut or permeable body surface= short diffusion path for metabolites - flatworms lack circulatory system

Why are flatworms poorly adapted to live on land?

They have a moist surface for gaseous exchange and lack skeleton against which locomotory muscles might act

Phylum Annelida

segmented worms, earthworms, leeches

Features of an earthworm

-Bilaterally symmetrical though round in transverse section- through one way gut (1 hole)

-One way gut allows regional specialisation - food is drawn into muscular pharynx, passed along an oesophagus to be stored in the crop, slowly released into muscular gizzard where it is crushed them digested and absorbed in the intestine - allowing ingestion of food to continue while previously ingested food is digested

-gas exchange takes place over moist body surface, to a blood circulatory system is required for the distribution of gases and food molecules

- it is metamerically segmented

- supported by a hydrostatic skeleton provided by segmented fluid filled body cavities

-locomotion relies on the action of muscles acting on hydrostatic skeleton, aided by external bristled of chitin called chaetae

- long and thin for ease of movement

Why do earth worms not require special organs for the exchange of respitroy gases?

Cylindrical shape provides a high surfsce to volume ratio and relatively low level activity means they have low rates of oxygen consumption

Phylum Arthropoda

arthropods - centipedes, millipedes, insects

Both aquatic and terrestrial

Insect body features

- bilaterally symmectrical

- one way gut, both mouth and anus allowing regional specialisation

- metamerically segmented and has different regions with a fixed number of segments in each region - head= 6 fused segments thorax= 3 abdomen= 11

- rigid exoskeleton of chitin over body to provide protection, degree of water retention and support. Muscles governing movement are attached internally to the exoskeleton of the joint limbs and to wings for flight

- presence of exoskeleton. Limits size of arthropods and creates a need for specialised gas exchange surfaces

- exoskeleton is covered in a waxy water resistant cuticle, a terrestrial adaption to further reduce desiccation - crustaceans lack as they are mostly aquatic

Phylum Chordata body features

-Bilaterally symmetrical, metamerically segmented and possesses a one way gut with mouth and anus and showing regional specialisation

- vertebral spinal column

- endoskeletion consists of internal joint system of calcified bones to which muscles for locomotion attach externally and

Evolutionary trends

- radical to bilateral symmetry which is a consequence of directional movement

- form a sac like gut cavity (enteron) to a through gut, providing the conditions for more efficient feeding and digestion, with one way processing of ingested food

- towards the development of intense blood transport system, the inclusion of a rigid skeleton and the possession of an impermeable outer covering, which is better adapted to a terrestrial existence

Why do some animals show radical symmetry while others have bilateral?

Animals which are sessile show radical symmetry allowing them to respond to enviromemt in all directions

Bilateral is associated with animals which move through their enviromemt in search for food