Kingdom Animalia

Question 1

What are the characteristics of animals?

Answer 1

• eukaryotic
• multicellular
• do not possess cell wall
• heterotrophs - feeding on organic food they digest internally
• capable of locomotion

Question 2

What Phyla do we need to know

Answer 2

Cnidaria, Platyhelminthes, Annelida, Arthropoda and Chordata

Question 3

Describe the body plan of cnidarians, Platyhelminthes and chordates

Answer 3

Simple organisms, eg cnidarian, have 3 simple layers – an inner gut, a middle endoderm and an outer ectoderm. Platyhelminthes have an increasing level of complexity with a mesoderm. Chordates have the greatest level of complexity with their mesoderm split by a coelom.

Question 4

List examples of Cnidaria

Answer 4

Sea anemones, jellyfish, corals and freshwater hydras

Question 5

What are the characteristic features of Cnidarians?

Answer 5

• They are diploblastic animals: they have two cell layers separated by mesogloea (a jelly-like, non-cellular layer).
• an outer layer ectoderm, which forms the epidermis
• an inner layer or endoderm, which forms the internal structures
• mesogloea is a non-cellular jelly-like layer through which cells are able to migrate
• There is little differentiation.
• The body is supported by the aqueous medium. They are restricted to an aqueous medium as they have no means of restricting water loss across their body surface.
• There is also a hydrostatic skeleton formed by the fluid filled enteron (gut cavity).
• Multicellular
• They have nematoblasts (stinging cells).
• They are radially symmetrical.
• They have tentacles.

Question 6

What forms do cnidarians exist in?

Answer 6

as a polyp or as a medusa.
A polyp spends most of its time attached to the substrate (such as a rock). It has a tubular body, usually with a mouth and a ring of tentacles on top. Eg Hydra and Sea anemones A medusa is a free-swimming bell- or saucer-shaped individual with a tube hanging down in the centre; the tube ends in a mouth and tentacles usually line the edge of the bell. eg jellyfish

Question 7

Give examples of Phylum Platyhelminthes

Answer 7

flatworms eg planarians and liver flukes

Question 8

What features are present in all Phylum Platyhelminthes?

Answer 8

•They are flat, unsegmented,
•They are bilaterally symmetrical. They have a front where sensory receptors can be positioned, allowing them to test the environment into which they are entering. The streamlined bilaterally symmetrical shape makes movement much easier compared to the radial symmetry of the cnidarians
•They are flattened dorsoventrally. This increase the surface area to volume ratio. This means that
oThey can increase their uptake of oxygen
oThey have a decreased diffusion distance from the body surface to body cells.
•They have well differentiated organ systems (e.g. for digestion). Each organ is made up of different types of tissue, which work together to carry out a specific role.
•They have three body layers ectoderm, mesoderm and endoderm (they are triploblastic) showing tissue differentiation but no body cavity (aceolomate). The mesoderm, found between the ectoderm on the outside and the endoderm on the inside, forms the bulk of the body and gives rise to many important body structures including true muscles.
•There is no specialised skeletal system but the mesoderm (mesenchyme) helps to support the body.
•They have a single opening to the gut – this means that the remains of food are passed out through the same body opening through which it enters.
•They are usually hermaphrodites with a complex reproductive system.

Question 9

What is a coelom?

Answer 9

Flatworms have only the gut or enteron. Most other triploblastic animals have a body cavity called the coelom. This is a fluid-filled space in which the organs are suspended. Without a coelom, flatworms have their organs simply crammed in the body, giving it a fairly dense and solid appearance.

Question 10

Why do flatworms not have a blood vascular system?

Answer 10

Blood vessels evolved from the mesodermal lining of the coelom and lie within the coelom, so flatworms have not evolved a blood vascular system. Their flattened shape, however, means that they have a large enough surface area to volume ratio for gases to be exchanged with the environment and transported in the body by simple diffusion alone.

Question 11

Describe what is meant by triploblastic

Answer 11

All animals except sponges and cnidarians develop from a three-layered embryo and are called triploblastic. The three body layers are the ectoderm, endoderm, and mesoderm. The mesoderm, found between the ectoderm on the outside and the endoderm on the inside, forms the bulk of the body and gives rise to many important body structures including true muscles. Whereas cnidarians show a tissue level of organisation, flatworms and all other animals (except sponges) have an organ level of organisation. Each organ is made up of different types of tissue, which work together to carry out a specific role.

Question 12

Give examples of Phylum Annelida

Answer 12

Annelids include earthworms, leeches and lugworms and inhabit aquatic and moist soil ecosystems

Question 13

What are the features of Phylum Annelida

Answer 13

• They are worm-like animals and are clearly segmented.
• They are triploblastic
• The mesoderm contains a body cavity ie a space (they are coelomate), within which lies the well differentiated digestive and other systems.
• They have well developed tissue differentiation.
• They are bilaterally symmetrical,
• they are metamerically segmented, typically long and thin, and the body is divided into a large number of structurally similar segments, each with its own body cavity. They have a blood and nervous system.
• A hydrostatic skeleton is formed from the segmental body cavities.

Question 14

What are the advantages of having a coelom within the body?

Answer 14

• Ratio of surface are to metabolically active tissue is increased. This is why annelids can be round in TS. There is not the same requirement to maximise surface area:volume for respiratory purposes.
• As the spaces are fluid filled, it can function as a very effective hydrostatic skeleton
• The muscles involved with locomotion are separated from the gut muscles. This allows movement of the organisms and peristaltic gut movements to occur independently
• It provides room for organ development

Question 15

Describe the feeding of annelids

Answer 15

They have a body cavity (the coelom), and they have a through gut (a gut with both a mouth and an anus showing regional specialisation). This has allowed different gut regions to carry out different digestive functions, improving efficiency e.g. a muscular pharynx, an oesophagus a crop (storage area) a muscular gizzard (for mechanical digestion) and an intestine for absorption. Digestion is extracelluar and nutrients are distributed by a well-developed circulatory system.

Question 16

Describe the segmentation of annelids

Answer 16

The most noticeable feature about annelids is the ringing of the body (Annelida means ‘ringed’). The ringing is called segmentation, and each ring is called a segment. Segmentation is an adaptation that improved their ability to burrow. This allows them to escape from predators, avoid adverse environmental conditions, and exploit new environments. However, in many other worms, certain segments contain specialised structures such as reproductive organs.

Question 17

How are warthworms adapted for locomotion and why?

Answer 17

Locomotion relies on the action of muscles acting on the hydrostatic skeleton aided by external bristles of chitin called chaetae. For ease of movement, earthworms are long & thin.

Question 18

What organisms are in Phylum Arthropoda

Answer 18

Insects and spiders

Question 19

What are the common characteristics of Phylum Arthropoda

Answer 19

• They display bilateral symmetry
• They have a fixed number of metameric segments – typically insects have 3 segments in thorax and 10-11 in the abdomen.
• Insects all have body plan with a clearly defined head, thorax and abdomen.
• Attached to the abdomen of insects are 3 pairs of jointed limbs
• They have compound eyes
• Like annelids, they have a through gut with a mouth and anus.
• Insects also have an exoskeleton composed of chitin – this can limit size of insect species but is an important terrestrial adaptation as it is waterproof.

Question 20

Why are arthropods the most successful group on earth?

Answer 20

Their body plan allows a vast range of features to be formed to suit any ecological niche. Whether it is the development of mouth parts for chewing (locusts) or into proboscis (green fly) or piercing skin (mosquitoes); large wings for efficient flight or stings to disable prey – the arthropods have evolved the means to cope in a vast range of habitats, and many have separate distinct body forms such as larval eg caterpillars and adult forms that have separate food sources.

Question 21

What is the body plan of an arachnid

Answer 21

Like insects spiders are bilaterally symmetrical and have a fixed number of metameric segments. However, they have 4 pairs of legs and their body has 2 main segments – the head and thorax and combined to form the cephalothorax

Question 22

What is included in Phylum Chordata

Answer 22

fish, amphibians, birds and mammals

Question 23

What are the common features of chordates

Answer 23

•Bilaterally symmetrical and metamerically segmented. In humans this is most easily recognised in the separate vertebrae of the vertebral column and associated with each vertebra, the paired spinal nerves arising from the spinal cord. Ie the backbone.
It may also be visible in some in the blocks of muscle in the abdominal wall – the “six pack”
•They are triploblastic, coelomate animals with three body layers (ectoderm, mesoderm, endoderm) with the mesoderm containing a body cavity within which lies the well differentiated digestive, reproductive, circulatory and excretory systems.
•They have an internal skeleton and a post-anal tail at some stages in their life cycle, which may be reduced or lost in some species.

Question 24

What does the name chordate reflect?

Answer 24

that they all have a notochord (a slender, stiff, but flexible dorsal rod running along the back) or spinal column. This slender rod of cells originating from the mesoderm runs along the back in the embryo of all chordates. It persists in primitive chordates, a very small group of relatively rare animals which are a bridge between the invertebrates and the vertebrates – these organisms have a notochord instead of a vertebral column. In vertebrates the vertebral column is either made of cartilage or bone. In cartilaginous fish, a cartilaginous skeleton forms a backbone, which is strong and rigid but also flexible skeleton. In bony fish, amphibians, reptiles, birds and mammals it is a skeleton of bone (spinal column). The skeleton consists of an internal jointed system of calcified bone

Question 25

Describe chordate segmentation

Answer 25

The segmentation of chordates is best described as a secondary adaptation for swimming. The S-shaped wiggle characteristic of swimming is produced by segmental muscle blocks or myotomes, which contract one after another in a serial pattern.

Question 26

Describe feeding mechanisms in chordata

Answer 26

Mammals may be active predators, omnivores or herbivores. The gut has both a mouth and an anus and consists of well-developed specialised regions. Digestion occurs extracellularly.

Question 27

What evolutionary trends do we see in the Kingdom Animalia

Answer 27

•From radial to bilateral symmetry
-radial symmetry is most evident in sedentary (sessile) groups, as it gives them the opportunity to obtain food from all directions.
-As groups become more complex – more movement is possible so bilateral symmetry becomes more evident. This allows the presence of anterior and posterior ends as well as a front and back (ventral and dorsal sides). This is more suitable for movement and allows the development of sense organs (receptors) at the front of the organism.
•The gradation from solid tissue between the body surface and the gut lining to the presence of cavities that reduce the amount of metabolically active tissue per unit volume.
•From an enteron gut cavity with only 1 opening to a through gut with a mouth and anus. The development of more advanced digestive systems, with regional specialisation allows for more efficient feeding and digestion.
•Development of internal circulatory systems, rigid skeletons and impermeable body coverings - important for life on land.