Biodiversity Of Animals

Question 1

phylogenetic tree

Answer 1

a diagram showing the evolutionary relationships between
ancestral groups or organisms and their descendants

Question 2

phylum

Answer 2

a taxonomic rank below kingdom and above class

Question 3

taxonomist

Answer 3

biologists that identify and group organisms according to their
characteristics

Question 4

6 animal phyla

Answer 4

●Porifera(sponges)
●Cnidaria(jellyfish,blue beetles)
●Platyhelminthes(tape worms)
●Annelida(earthworms)
●Arthropoda(insects,crab,spider,locust)
●Chordata(mammals,birds,amphibians, reptiles, fish)

Question 6

Important features of body plans include:

Answer 6

 body symmetry and cephalisation
 tissue layers
 number of gut openings
 the presence of a body cavity

Question 7

cephalisation

Answer 7

the presence of a definite head that contains sense organs in
animals; first seen in the phylum Platyhelminthes

Question 8

sessile

Answer 8

organisms that are immobile and attached to one place for life,
e.g. sponges and barnacles

Question 9

gut

Answer 9

portions of the alimentary canal

Question 10

Two main groups in Kingdom animalia

Answer 10

●Vertebrates
●Invertebrates

Question 11

Invertebrate

Answer 11

Animals without a vertebral column

Question 12

Vertebrate

Answer 12

Animals with a vertebral column

Question 13

asymmetry

Answer 13

no symmetry, i.e.
they cannot be
divided into two equal
halvese.g.: amoeba,
sponges

Question 14

radial symmetry

Answer 14

usually sessile or are
able to move around
only a little
e.g.: Cnidaria

Question 15

bilateral symmetry

Answer 15

 body plan can be
divided into two equal
halves in only one
plane. i.e. they have a
left side and a right
side that are identicalcannot be divided into
an equal anterior
(front) and posterior
(back) end,e.g. all other phyla
except Porifera and
Cnidaria

Question 16

The first tissue layers formed in the embryo are

Answer 16

germ layers

Question 17

diploblastic

Answer 17

having a body wall that is composed of two layers: the
endoderm and ectoderm

Question 18

triploblastic

Answer 18

any organism that develops from a three-layered embryo;
ectoderm, mesoderm and endoderm

Question 19

coelom

Answer 19

a fluid-filled cavity that lies between the ectoderm and
endoderm and is found in triploblastic organisms

Question 20

hydrostatic
force

Answer 20

a force exerted by a liquid, usually water, increased with
constriction and gravity

Question 21

peristalsis

Answer 21

an automatic wave of muscle contraction and relaxation that
moves food in one direction through the digestive tract

Question 22

Primary germ layers

Answer 22

The primary germ layer consists of the ectoderm (outer layer) and the endoderm
(inner layer).
 The ectoderm will develop into the skin or epithelium and the nervous system
of the animal.
 The endoderm will form the digestive system.
 Animals that only have two germ layers (ecto- and endoderm) are called
diploblastic animals (Figure 5).
 Diploblastic animals do not form complex organs and are more primitive
animals.

Question 23

Secondary germ layers

Answer 23

The mesoderm is a secondary germ layer which develops between the endoderm
and the ectoderm.
diploblast triploblast
ectoderm
mesoderm
endoderm
81
 Animals that have three tissue layers (i.e. ecto-, endo- and mesoderm) are
called triploblastic animals. Figure 5 illustrates these three tissue layers.
 The mesoderm develops into connective tissue, bone, blood, reproductive
organs, cartilage, blood and the lymphatic systems.

Question 24

One
opening

Answer 24

Animals with only one opening to the gut will consume food through
the opening (mouth) and excrete waste through the same opening.
There is only one opening for both the mouth and the anus (Figure 6).
 A one-opening to the gut is also called a blind-ending gut.
 This limits the amount of food that these animals can consume –
they must excrete the waste from their digestive system before
they can consume more food.

Question 25

Two openings

Answer 25

Animals with two openings to the gut can consume food through a mouth opening and excrete waste through another opening called the anus (Figure 7). This type of gut is also called a through-gut.  A through-gut is an advantage because food can be consumed continuously because it moves through the digestive system.  Sections of the digestive system can also specialize (e.g. stomach) to improve the efficiency of the digestive process.

Question 26

Coelom (body cavity)

Answer 26

A coelom is a body cavity that develops inside the mesoderm tissue layer in more advanced animals

Question 27

Acoelomate

Answer 27

An acoelomate animal does not have a body cavity or coelom . Acoelomate animals may be either diploblastic or triploblastic. Acoelomate animals are usually smaller and are less mobile that coelomates

Question 28

Coelomate

Answer 28

Coelomate animals have a body cavity or coelom in their mesodermal tissue layer (Figure 8B)

Question 29

pseudocoel

Answer 29

some triploblastic organisms have a body cavity that is not surrounded by mesoderm.

Question 30

Advantages of a coelom

Answer 30

 Allows more complex organs to develop such as digestive organs, muscular system, blood system etc.  Allows the creation of a hydrostatic force to be generated for movement in soft-bodied animals  It separates the endoderm and ectoderm from each other with a cavity which allows the layers to move independently of each other. This allows peristalsis to occur  In some organisms, the coelomic fluid (fluid found in the coelom) helps to transport nutrients and waste in the body

Question 31

spicule

Answer 31

a minute (very small) sharp-pointed object or structure that is typically present in large numbers, found in sponges

Question 32

Phylum Porifera

Answer 32

 aquatic (live in water)  asymmetrical with no cephalisation  function at a cellular level  acoelomate  no openings to the gut  sessile organisms that feed by filtering out floating particles from the water column (Figure 9)  the body is made up of millions of spicules which protect and support the sponge

Question 33

Phylum Cnidaria

Answer 33

 aquatic, mostly marine but some live in freshwater habitats  radially symmetrical with no cephalisation  diploblastic which means they have a cellular ectoderm and a cellular endoderm.  they also have an acellular jelly-like layer between these two layers called the mesoglea.  acoelomate  one opening to the gut that acts as both the mouth and the anus. the mouth often has tentacles that help catch prey.  Cnidarians occur in two different body forms: o a sessile polyp phase (Figure 10) o a free-swimming medusa

Question 34

Phylum Platyhelminthes

Answer 34

 most are internal parasites but some are aquatic and free-living  bilaterally symmetrical with cephalization – a definite anterior, posterior, dorsal and ventral side because they are bilaterally symmetrical (Figure 12)  dorsoventrally flattened which means they appear squashed from the dorsal to the ventral side  have their sense organs and nerve tissue concentrated in the anterior region of their body (cephalisation) which allows them to detect what lies ahead of them – aids in feeding and avoiding danger  triploblastic which allows them to develop tissues and organs e.g. nervous tissue and reproductive organs  acoelomate and therefore no circulatory system  one opening to the gut – the digestive cavity branches around the body to transfer nutrients around the body

Question 35

Phylum Annelida

Answer 35

 aquatic (freshwater and marine) and terrestrial habitats  bilaterally symmetrical with cephalisation  triploblastic  coelomate - coelom is a fluid-filled cavity that is used as a hydrostatic skeleton for movement  segmented which means their bodies consist of repeating segments, called metameres

Question 36

Phylum Arthropoda

Answer 36

 aquatic (freshwater and marine (Figure 15)) and terrestrial  bilaterally symmetrical with cephalisation  triploblastic  coelomate – the coelom is filled with a fluid, which acts like blood, called a haemocoel. arthropods therefore have an open circulatory system  more advanced segmentation of body parts so that each segment has a particular form and function i.e. abdomen, thorax and head  all arthropods have jointed appendages that are used for movement and feeding  two openings to the gut (a through-gut)  a waterproof exoskeleton made of chitin The exoskeleton:  protects the arthropod from drying out  prevents diffusion of gases across its waterproof surface; arthropods have therefore developed gaseous exchange organs such as gills and lungs  does not grow as the arthropod grows and it must be shed regularly (ecdysis) and regrown; the arthropod is vulnerable during regrowth of the exoskeleton because it is weaker and requires a lot of energy

Question 37

Phylum Chordata

Answer 37

 aquatic (freshwater and marine) and terrestrial  bilaterally symmetrical with cephalisation  triploblastic  coelomate  segmented body  two openings to the gut (through-gut)  all vertebrates have a rod-like support named a notochord which may develop into the vertebral column (Figure 16)  have a hollow dorsal tubular nerve cord (spinal column) which often forms the anterior brain (e.g. humans)  initially develop pharyngeal gill slits that disappear in terrestrial chordates at adulthood  have a post-anal tail  Chordata can be ectothermic or endothermic. The body temperature of exothermic animals is regulated by the external environment whereas the body temperature of endothermic animals is regulated by internal metabolic reactions. Examples of endothermic animals are humans and birds