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Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 1
Variety of Life
Syllabus : . The relationship between the diversity of organisms and the variety of their ways of life.
To use a range of organisms found in two different local habitats (preferably, one terrestrial habitat
and one aquatic habitat) to illustrate how the organisms are adapted to their habitats and ways of
life.
Introduction
All things on the earth can be classified as below:
All Things
Non-living things
Living organisms
Virus
Eukaryotes
(not cellular)
Protoctista
(e.g. protozoa)
Fungi
Plantae
Prokaryote
(e.g. bacteria)
Animalia
We cannot define precisely what life is or whence it came. All that we can do is
to describe the observable phenomena that distinguish living matter from non-living
matter. These are
1. Nutrition : all living organisms need food, which is assimilated and used as a
source of energy.
2. Respiration : all life processes require energy. The energy is released during
breakdown of certain energy-rich compounds by the process of
respiration.
3. Irritability : living organisms have the ability to respond to changes in both the
internal and external environments and thus ensure that they
maximize their chances of survival.
4. Movement : animals are distinguished from plants by their ability to move from
place to place, that is they locomote. This is necessary in order for
them to obtain their food, unlike plants which can manufacture their
own food from raw materials obtained in one place.
5. Excretion : it is the removal of waste products of metabolism from the body; the
removal of certain unusable materials absorbed by the organisms, such
as lead, radioactive dust can be regarded as excretion.
6. Reproduction : the life span of organisms is limited, but they all have the ability
to perpetuate 'life', thereby ensuring the survival of the species.
7. Growth : non-living objects, grow by the addition of new material to their outside
surface, e.g. crystal; living organisms grow from inside the body, the
molecules are formed into new living protoplasm during the process of
assimilation.
These seven characteristics can be observed in all living organisms and are our
only means of indicating whether life exists or not.
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 2
Relationship between the diversity of organisms and the variety of their ways of life
Apart from the non-living things, the others, viruses and living-things live in
their own ways, variety of ways.
Virus :
They are on borderline between living and non-living things because they can only
reproduce in the host cell but show no characteristics of life when outside. Thus they
are obligate parasite, i.e. they can only live parastically.
Example selected : a bacteriophage
Structure :- There are many varieties of bacteriophages. Some are spherical or rod shaped, others
may have a hexagonal head with a tail.
- Components : head >> contain one strand DNA enclosed by protein coat.
DNA strain >> the genetic material forming the core of the phage.
sheath >> contractile to inject the DNA strain into the host cell.
tail fibres >> fit into the receptor sites on bacterial cell surface.
baseplate >> break the bacterial cell wall with the aid of lysozyme.
*****
insert B.S.I p.19 fig2.16
*****
Fig. 1 Structure of a bacteriophage
Life cycle :- The initial stage is the attachment of the virus to the host cell by its tail.
- An enzyme (lysozyme) in the tail digests part of the bacterial cell wall and the DNA
in the head passes into the bacterial cell whereas the protein coat of the head and tail
remained outside.
- Then the viral DNA directs the biosynthetic systems of the host cell to produce new
viral DNA and viral protein.
- Finally, about 30 minutes later, the infected bacterial cell bursts and several hundred
newly formed viral particles are released, ready to attack new bacterial cells.
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 3
****
insert B.S. I p20 fig2.17
*****
Fig. 2 Life cycle of a bacteriophage
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 4
Exercise : (96 I 1)
The schematic diagrams below show the different stages (P,Q, R, S and T) in the life
cycle of a bacteriophage. They are NOT in the correct sequence.
(a) Rearrange the stages by listing the letters only to show the correct sequence of
events in the life cycle of a bacteriophage from attachment to lysis. [1 mark]
(b) Identify X and Y. Describe the events illustrated by stage T. [2½ marks]
(c) Describe the events illustrated by stage P.
[1½ marks]
3. Comparison of virus with plant or animal cell :
Virus
Protein coat enclosing nucleic
acid,
Plant or animal cells
More complicated with many
organelles
Genetic
materials
DNA / RNA
DNA
Metabolism
Nil
Enzymes presence to catalyse
different metabolic activities
Life span
After being isolated from the
host cells can exist indefinitely
Definite
Structure
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 5
Bacteria:
There are four main types :
Cocci >> these are spherical-shaped bacteria,
（球菌）occurs in pairs called diplococci, e.g. Pneumococcus
occurs in chains called streptococci, e.g. Streptococcus
occurs in a bunch of grapes called staphylococci, e.g. Staphylococcus
Bacilli >> these are rod-shaped bacteria.
(桿菌） e.g. Bacillus, Escherichia coli (in alimentary canal),
Clostridium tetani
Spirilla >> these are spiral-shaped bacteria, e.g. Spirillum
（螺旋菌）
Vibrio >> these are comma-shaped bacteria, e.g. Vibrio cholerae
（弧菌）
Example selected : Bacillus
****
insert B.S.I p5 fig 2.3
****
Fig. 3 A generalized Bacillus.
[Note] Bacteria can be classify into two major groups :
i. Gram-positive bacteria : the cell wall retains a blue-black stain after Gram stain and
easily destroyed by antibiotics.
ii. Gram-negative bacteria : the cell wall retains a pink stain after Gram stain and
resistance to antibiotics.
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 6
Heterotrophs
- Bacteria that break down dead organic matters to obtain food are saprophytes.
- Most disease-causing bacteria are parasites. e.g. Mycobacterium tuberculosis
causing tuberculosis.
- Mutualistic bacteria :
(i) nitrogen-fixing bacteria in the root nodules of leguminous plants provide
nitrate for the plants and obtain carbohydrates from the plants.
(ii)
Escherichia coli in human intestine produce vitamins for human and
obtain carbohydrates from man.
- Denitrifying bacteria living in oxygen deficient condition (e.g. water logged soil).
They obtained energy from anaerobic breakdown of sugar and convert nitrate
into ammonia, nitrogen or oxygen.
Autotrophs :
- Photosynthetic bacteria using H2S (instead of H2O in higher plant) to carry out
photosynthesis.
- Chemosynthetic bacteria derive energy from inorganic molecules such as ammonia,
nitrate or sulphur, etc. e.g. Nitrosomonas convert ammonia into nitrite.
How bacteria reproduce
- Usually they reproduce by binary fission.
- Under unfavourable conditions, thick-walled spores which are highly resistant to
drought or extreme temperature are produced.
Economic importance :
(i) Disease causing e.g. Tetanus（破傷風）, galls and blights（枯萎病）of trees,
(ii) Deterioration of stored food and damage to buried metal pipes
(iii) As decomposer to recycle the organic matters e.g.Nitrosomonas convert NH 3 into
nitrites.
(iv) Supplying nitrate to plants, e.g. nitrogen-fixing bacteria in the root nodules of the
leguminous plants convert the atmospheric nitrogen into nitrates.
(v) Help in digestion, e.g. E.Coli living in the alimentary canal of herbivores
produces cellulase to digest cellulose.
(vi) Produce Vitamins, e.g. Bacillus subtilis occur in the intestine of man and is
responsible for the production of vitamin B 1 2 . Some other species may also
produce vitamin K.
(vii) Produce food, e.g. Yoghurts and cheese are made from milk by bacterial
activities of Lactobacillus. Vinegar is a product by the activity of Actobacter.
(viii) Produce chemicals, e.g. alcohol and acetone, antibiotic, amino acids, hormones
(ix) As they easily cultured and may be used for research, especially in genetics.
Fungi :
Their cell wall is composed of a polysaccharide, chitin(absent in plant cells). They
have no chlorophyll and are therefore unable to photosynthesise. They feed
heterotrophically, either saprophytic (feeding by rhizoids) or parasitic (feeding by
haustoria). They reproduce by means of spores.
Example selected : Rhizopus -- bread mould
- they are saprophytic, feed on dead organic matters such as bread, rice and fruits
- the feeding hyphae, which penetrate the substratum, secrete hydrolytic enzymes to
digest the organic matters to soluble and diffusible forms (extracellular digestion)
- the mycelium is branching for providing large surface area for absorption of food
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 7
insert BSI p35 fig. 3.5a
Fig. 4
Mycelium of Rhizopus as seen with LP of light microscope
Economic importance of the fungi :
(i) increase soil fertility and used in sewage disposal, e.g. saprophytic fungi (work
together with saprophytic bacteria) able to decompose dead organisms and animal
excreta to simple inorganic materials
(ii) used in brewing industry and baking industry, e.g. yeast
(iii) antibiotics formation :e.g. Penicillium produce useful penicillin
(iv) certain fungi are particularly suitable for use in the study of genetics
(v) act as food sources, e.g. mushroom are edible which are rich in protein
(vi) cause food spoilage, e.g. Mucor and Rizopus
(vii) deterioration of materials.
(viii) food poisoning, e.g. poisonous mushrooms
(ix) causing diseases, e.g. ringworm, athlete’s foot
Exercise :
(90 I 1)
Give the appropriate taxonomy group for the organism which cause the following
human diseases : cholera ,malaria, measles, syphilis, rabies, influenza, athlete's foot,
hepatitis.
[4 marks]
(97 I 1b is also being classified into topic 'Nutrition')
With reference to TWO morphology features, describe how these enable a saprophytic
mould to adapt to its way of life.
[2 marks]
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 8
Algae :
They are considered as the most primitive plants. They are classified as a sub-kingdom
in the Plant Kingdom. The common characteristics of this group are :
(i) They are not differentiated into, stem and leaf, and no vascular tissues is found.
(ii) Most are aquatic, although a few are found in moist terrestrial conditions e.g. on
soil and on bark of trees.
(iii) They all contain photosynthetic pigment although in many species the green
colour of this pigment is masked by the presence of other pigments.
(iv) They display considerable diversity of forms i.e. unicellular, colonies, branched
and unbranched filaments, sheet-like thalloid forms are all represented within the
phylum.
Example of a thalloid brown alga selected : Fucus
It widely distributed along sea coasts between tidal levels (inter-tidal zone),
predominantly along the coasts of temperate seas. The reserve food is a kind of
complex carbohydrate called laminarin but not starch . The brown colour is due to
the presence of a brown pigment fucoxanthin which is associated with the
chloroplast masking the chlorophyll.
[Note] This is an adaptation to photosynthesise under water because fucoxanthin strongly absorbs
blue light, which penetrates water much further than longer wavelengths
BSI p48 fig 3.18
Fig. 5 External features of Fucus
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 9
Exercise : (97 I 1a)
With reference to two morphological features, describe how a thalloid brown alga
adapt to its way of life.
[2 marks]
Biological Significance of Algae :
1. Food source : some of the kelps are used as food in China and Japan e.g. Porphyra
2. Fertilizers : ash obtained by burning kelps is an excellent source of iodine and
potassium (but poor in nitrogen and phosphorus, so are of limited use)
3. Carbon fixation : contribute half of the world’s productivity is come from algae
4. Maintain air composition : oxygen is a by-product of photosynthesis
5. Sewage disposal : useful in open ‘oxidation ponds’ which are used especially in
tropical and subtropical countries, the algae grow aerobically on
the raw sewage, the algae can also be harvested and processed for
animal fodder
6. Research : unicellular algae show all the typical plant characteristics and often
make ideal research since they can be grown in large numbers under
precisely controlled conditions without occupying a great deal of space
7. Produce other useful substance, e.g. agar form non-toxic gels used as thickeners
8. Algal bloom : under extra nutritive and warm condition algae produce ‘blooms’, i.e.
explosive growth, since the amount is far more than usual therefore
they die before being eaten, this provide good food source for aerobic
bacteria to multiply that in turn deplete the water oxygen, so lead to
death of the fish and other organisms
: toxins produced by algal blooms may stored in shellfish that feed on
the algae, and then may passed on to man causing paralytic shellfish
poisoning
: algae also cause problems in water storage reservoirs where they grow
on and block the beds of sand used as filters
Plant Kingdom :
A. Phylum Bryophyta
Fig. 6
Structure of Polytrichum.
BSI p57 fig. 3.25
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 10
- they grow on damp soil between other plants which may afford its shade
- able to colonise the sites of old bonfires remarkably quickly
Limitation to terrestrial habitat :
• sperms are flagellated and must swim in a liquid medium to the archegonia
• there are no special supportive structures and conductive tissues, so the
plants are restricted in damp soil
• they are dependent on the availability of water and mineral salts close to or
at the surface of the soil, because they have no true roots for penetration
Adaptation to terrestrial habitat :
• the spore are released by wind
B. Phylum Filicinophyta (Ferns)
BSI 3 r d Ed. P42 fig. 2.37a
Fig. 7 External features of the sporophyte generation of Dryopteris filix-mas, the male fern. The
small diagrams on the right showing the details of one pair of pinnae and the sori on the
underside of the frond
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 11
They are very ancients group of plants, they are the earliest known vascular plants.
The general characteristics of this group of plants are :
1. Vascular tissue present (xylem and phloem) in sporophyte , sporophyte therefore
has true roots, stems and leaves.
2. Leaves relatively large and called fronds.
3. Haploidy spores produced in sporangia which are usually in cluster called sori.
Fig. 13 LS of sorus of Dryopteris filix-mas showing details of sporangium and spore dispersal.
BSI 3 r d Ed. P44 fig. 2.38a
Fig. 8 External features of the gametophyte generation of Dryopteris filix-mas. The prothallus is
green and photosynthetic. It has no vascular tissue and no protective cuticle.
Exercise : (99 I 1)
The Photograph below shows the undersurface of an aerial part of a non-flowering
plant at the reproductive stage :
(a) Name the organ found inside structure 1 and state its roles in the life cycle of the
plant.
(b) State the ploidy number of the organ.
[3 marks]
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 12
Adaptation of ferns to terrestrial environment :
- the roots, conductive tissues (xylem tracheids and phloem) and mechanical tissues
are more or less well developed
- the water-proof cuticle (absent in the prothallus) on the leaves of the sporophyte
allows them to inhabit drier habitat than the bryophytes
[Note] the fertilization process in the gametophyte still requires the presence of water for the
antherozoids to swim towards the archegonia
- the asexual reproduction in the sporophyte shows full adaptation to dry condition in
the formation and the dispersal of the spores
Exercise : (94 I 1)
Mosses and fern are often found in different habitats. Describe the respective habitats
of these two types of plants. What features of these plants are associated with their
existence in their habitats ?
[5
marks]
C. Spermatophyta (Seed plants) :
The most successful group of land plants are the Spermatophyta.
Table 1 Classification and characteristics of the Spermatophyta.
BSI 3rd Ed. P41 table2.10
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 13
I/ Gymnosperms :
They are trees or shrubs, mostly evergreen with needle-like leaves. The largest
group are the conifers, a group containing trees which are found at higher
altitudes and further north than any other trees.
Example of conifer selected : Pinus
Morphology :- the tree of Pinus (pine) is a tall erect evergreen tree has green needle-like leaves, and
have the following characteristics to adapt the dry conditions :
•
sunken stomata : to reduce the rate of transpiration
•
cutinized epidermis : to reduce water evaporation
•
needle shape : to reduce the surface area, in turn reduce water loss
•
sclerenchyma : to form supportive tissue which helps the leaves in an erect
position to receive sufficient sunlight
- the tree has a well-developed tap root and numerous aerial branches
Fig.9 External features of the sporophyte generation of Pinus sylvestris, the Scots pine.
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 14
Adaptation to land habitat :- the pine tree shows an obvious step towards a fuller adaptation to dry habitat than the
bryophytes and ferns
i/ it has normal roots that penetrate deep into the soil for the absorption of water
ii/ the pine also has normal erect stem that develops mechanical tissues necessary
for support, and vascular tissues necessary for the translocation of materials
iii/ the needle shaped leaves have a relatively small area for transpiration
iv/ water loss is further reduced by a heavy layer of cutin on the leaves and a
suberized bark on the trunk
[Note] Cutin and suberin are fatty materials which are impermeable to water and gases.
v/ the reproductive processes don’t need the presence of water, the male gamete is
transferred to the female gamete by wind and then through a pollen tube
II/ Angiosprems :
The members of this class (herbaceous or woody) form the dominant vegetation
in the world today and are mainly terrestrial with some aquatic. They adapt to life
on land better than any other plants .There are two classes : monocotyledones and
dicotyledones
Table 2 Major differences between dicotyledons and monocotyledons
BSI 3 r d ed. P46 fig 2.11
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 15
Example of a herbaceous monocotyledon selected : grass (Festuca pratensis)
BSI 3 r d Ed. P48 fig2.41
BSI 3 r d ed. P48 fig. 2.41
Fig.10 Vegetative and floral morphology of the grass (Festuca pratensis).
(a) Vegetative morphology. (b) Floral morphology - the inflorescence. (c) Detail of one open flower or floret.
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 16
Example of herbaceous dicotyledon selected : creeping buttercup (Ranunculus repens)
Fig.11 Vegetative and floral morphology of the creeping buttercup (Ranunculus repens). It is a perennial plant, found
in wet fields.
BSI 3 r d Ed. P49 fig. 2.42
BSI 3 r d Ed. P49 fig. 4.42
Protozoans :
They are sometimes are classified as a phylum of animals because of their motile
properties, however, some biologist classified them as a separate Kingdom Prostia
with other unicellular organisms because of their simple organization (with
specialized organelles, but no tissue or organs) and the following characteristics :
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 17
Example selected : Paramecium
A well known ciliate that feed on bacteria, smaller protozoa, algae and yeast. They
live in stagnant water, or slow-flowing fresh water containing decaying organic matter
since these are the food of bacteria. They posses a constant elongate body shape with
blunt anterior end and a tapered posterior.
Fig.12 Paramecium - structure visible under the light microscope (350x)
UB p93 fig7.14
Osmoregulation:- there are two definite contractile vacuoles, each is fed by radiating canals from
various parts of the body and empty it into the contractile vacuoles
- the contractile vacuoles discharge their content outside at certain time interval
depends on the water potential difference between the medium and the cytoplasm
Importance to man :Malaria is a common disease in tropical countries. It is caused by the mosquito
parasite Plasmodium falciparum, a type of protozoan.
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 18
Animal Kingdom :
A. Cnidarians (coelenterates):
The majority of animals in this class are marine, but genus Hydra is found in fresh
water.
Example selected : Obelia :
The body of Obelia is made up of two layers (diploblastic), ectoderm and endoderm
which separated by a thin, jelly-like layer (the mesogloea). The cavity is called an
enteron.
BSI 3 r d ed. P55 fig. 2.48b
Fig. 13 Obelia - a marine, colonial cnidarian with two types of polyp and a medusoid form
Exercise : (98 I 1) (also belong to topic' Echinodermata')
A biology student was given a variety of specimens belonging to the following
taxonomic groups :
(a) Echinodermata
(b)
Cnidaria
List TWO characteristic features that the biology student should look for in each
of the specimens to confirm its identity as a member of either of the above groups.
Tabulate your answers.
[4 marks]
[Note] While the protozoa have a cellular level of organization, and the cnidarians are said to have a
tissue level of organization.
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 19
B. Platyhelminthes (flatworms) :
The Platyhelminthes are commonly known as the flatworms, as they are
dorso-ventrally flattened. They have only a single opening in the digestive tract. In
contrast to the cnidarians, the flatworms have a third body layer, the mesoderm,
between the ectoderm and endoderm, and this body plan is known as triploblastic.
There is no body cavity between internal organs, acoelomate.
Table. 3 Classification and characteristics of the phylum Platyhelminthes (flatworms)
BSI 3 r d ed. P57 table 2.14
Special features :Regeneration : it can regenerate a complete animal when they are cut into pieces, but
the nervous system should remain intact
Hermaphrodites : possess both female and male reproductive organs, so
self-fertilization is possible, but cross-fertilization is more usual,
fertilization is internal.
[Note] It can also produce asexually.
Triploblastic : there are third germ layer -mesoderm
C. Annelida :
The annelids are segmented worms. The majority are marine animals of shallow
water. Some are free-swimming. The most distinguish characteristic of this phylum
is the division of the body into similar segments - metameric segmentation.
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 20
Special features :Coelom : it is the body cavity that separates the body wall from the alimentary tract
and the space are filled with fluid
: functions
a/ act as a hydrostatic skeleton
b/ enable activities of the body wall and alimentary canal to operate
independently of each other
c/ permit animals to become much larger
d/ the fluid of the cavity may act as a circulatory medium for the transport
of food, waste materials and gases
e/ waste materials and excess fluids may be temporarily stored here
f/ provides space for the enlargement of internal organs
g/ may play a part in the osmoregulatory activity of the organisms
Metameric segmentation : typically every segment is exactly similar,
: although the segments are partitioned from one another,
they do not function as independent units, but are
co-ordinated as integral parts of the body
: there is for each species, a more or less definite limited
number of segments
: it provides an opportunity for specialization in certain
segments without interference with others
[Note] the repeated proglottides in the tapeworm (Phylum Platyhelminthes) are differ
from the segments in the annelids
i) each of the proglottides are identical
ii) the number of proliferated proglottides is very large and apparently unlimited
iii) they are not co-ordinated to work in harmony
iv) the most mature segments are at the posterior and whereas in metameric
segmentation, the anterior segments are the first to mature
Exercise :
(93 II 5)
Compare and contrast the body organizations of a hydroid coelenterate, a tapeworm
and an earthworm. Explain the significance of the differences you have
described.[20 marks]
(96 I 3)
What are the advantages of the body organization of an earthworm over that of a
planarian ?
[ 5 marks]
Example studied : earthworm
The earthworm (belong to class Oligochaeta) live in the superficial layer of soil rich
in decayed matter. The earthworm do not come out at daytime unless a heavy rain
floods the burrow. They come out only at night to feed and to mate.
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 21
Fig. 14 Ventral view of anterior region of Lumbricus terrestris (earthworm)
Adaptation to the terrestrial environment :Earthworm is a terrestrial animal, but it is considered as unsuccessful to terrestrial
environment because of the following reasons :
1. The skin is permeable to water so that the earthworms are constantly threatened
by desiccation. They cannot survive in dry condition
2. The hydroskeleton of the earthworm cannot raise the body off the ground so that
there is friction between the ventral surface of the body and the substratum
during movement.
3. Movement is by the peristalsis of muscles existing in layers. Such movement is
relatively slow when compared with the insect or human where movement is by
lever systems operated by muscles existing in bundles
Economic importance :They contribute to soil formation and improvement in the following ways
1. Tunnels improve aeration and drainage.
2. Dead vegetation is pulled into the soil where decay by saprophyte takes place.
3. Mixing of soil layers. Addition of organic matter by excretion death.
4. Secretions of gut neutralize acid soils.
5. Improving tilth by passing soil through gut.
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 22
Exercise : (99 I 5)
For each of the following features name ONE taxonomic group that possesses it. State
ONE function of the feature that aids the survival of the organisms in that group.
(a) hydroskeleton
(b) nematoblast
Tabulate your answers.
[4 marks]
D. Arthropoda (jointed-leg animals)
Arthropods are the most diverse group of animals, occurring in almost every
ecological niche, and also surpassing all other animals in their number of species
and individuals. They are thought to have evolved from some annelid-like
ancestors.
Example of crustacean selected : crab
- common on rocky shores and beaches
- respired by gills
- External morphology
• the body comprises a rigid cephalothorax (head + thorax) and a short abdomen
folded forwards under body
• the first three pairs of thoracic appendages, called maxillipeds, are involved in
feeding but are not visible from the dorsal surface
• with two pairs of antennae, a pair of compound eyes raised on stalks
Fig. 15 Dorsal view of a crustacean Carcinus maenas, the shore crab.
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 23
Example of insect selected : butterfly
- insects are flying invertebrates, contains more than 800,000 species (the largest
group of animals), they are considered as the most successful group of animals as
they have occupied virtually all environmental niche on land and can inhabit the
driest habitat
- life cycle of butterfly is complete metamorphosis which incolves eggs, larva, pupa
and adult four stages
- External morphology
• well-defined haead, thorax abdomen
• with one pair of antennae and three pairs of mouthparts
(a)
Fig. 16 (a) Dorsal view of an insect Pieris brassicae, the white butterfly, with wings shown on one side and lefs the other.
(b) Detail of head of Pieris brassicae
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 24
Economic importance of insects :• insects are important components of terrestrial and fresh-water food webs and
many of them are important scavengers removing organic wastes
• many insects, e.g. bees, are pollinator of fruits and crops useful to man
• insects may also be pests of man, his cultivated plants and domesticated
animals, they may cause damage or disease directly, e.g. locusts, etc.
• insects may be vectors of pathogens, e.g.(i) mosquito carries Plasmodium, the
protozoan causing malaria, (ii) rat flea carries the bacteria causing bubonic
plague
• insects may damage stored food (e.g. cockroaches) and wooden materials (e.g.
termites)
• insects are used in the biological control of pests, albeit often against other
insects, e.g. ladybirds eat aphids
• also used in scientific experiments, e.g. Drosophila (fruit fly) in the study of
genetics
• provide sources of products useful to man such as beeswax, honey and silk, etc.
E. Mollusca :
The members characteristically have a soft body, which is often protected on the
outside by a shell. They are mostly marine, living along seashores or in shallow
water, but some are terrestrial and few are parasites. Examples are snail, slug,
mussel, oyster, cuttlefish, squid, and octopus.
Economic importance :1. Shellfish, oysters, are important food sources for man.
2. The shell of molluscs have been used for jewellery, currency and tools.
3. The adults and the larvae are important links in food webs.
4. The shipworm bores holes in submerged wooden structures such as boats.
5. Snails are intermediate hosts for some important parasites, e.g. Fasiola that
causing liver rot in sheep.
Example of bivalve selected : (clam)
Fig. 17 Lateral view of a clam
Fig. 18 Internal structure of a bivalve (scallops)
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 25
F. Echinodermata :
All are marine and are largely bottom-dwellers inhabiting shallow seas. The adult
forms exhibit pentamerous symmetry ( a form of radial symmetry). Their most
unique characteristic is the possession of a water vascular system, derived from the
coelom, and tube feet, which may end in suckers, for locomotion. Spines, which
may be movable, usually present. e.g. starfish, sea urchin and sea cucumber.
Example selected : starfish
Fig. 19 Asterias, the common starfish. One arm is turned to show the lower side. Circles contain magnified views.
Exercise : (98 I 1)
A biology student was given a variety of specimens belonging to the following
taxonomic groups :
(c) Echinodermata (b) Cnidaria
List TWO characteristic features that the biology student should look for in each of the
specimens to confirm its identity as a member of either of the above groups. Tabulate
your answers.
[4 marks]
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 26
G. Chordata :
They generally exhibit a greater complexity of structure and a higher degree of
organization than any other group in the animal kingdom. This increased
complexity has necessitated an increase in size, and the mean size of chordates is
accordingly larger than the mean size in any other phylum. They are found on land,
in the sea and freshwater, and also in the air.
Characteristics of classes in Vertebrata :
I/ Class Osteichthyes (bony fish)
¾ Skin with scales (thin, round and made of bone)
¾ Paired pectoral and pelvic fins, symmetrical tail fin
¾ Visceral clefts present in adult as gill, but covered by operculum
¾ Lateral line system well-developed
¾ No external and middle ear; heart with two chambers
¾ Streamlined body, this offer little resistance to forward movement in water
¾ External fertilization; eggs produced
¾ Poikilothermic
Example selected : Clupea harengus (herring)
Fig. 20 Laterl view of a common fish.
II/
¾
¾
¾
¾
¾
¾
¾
¾
Class Amphibia
Soft moist skin can be used for gaseous exchange to supplement lungs, no scales
Two pairs pentadactyl limbs
Visceral clefts present in aquatic larva (tadpole) only, lungs in adult, which is
usually terrestrial
Lateral line system in tadpole only
No external ear only; heart with 3 chambers (two auricles and one ventricle)
With two nostrils that connected to mouth cavity and with valves which exclude
water
Eyes often with movable lids ; eardrums externally placed on toads and frogs
Tongue often protrusible.
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 27
¾
¾
¾
¾
Respiration by gills, lungs, skin or the mouth lining, separately or in combination;
Metamorphosis from larva to adult in life cycle
External fertilization; egg produced
Poikilothermic
Example selected : Rana (frog)
Life form and function p65
Fig. 22 A typical frog.
III/ Class Reptilia
¾ Body covered with dry cornified skin (not slimy), usually with scales.
¾ Two pairs of limbs, each with four toes ending in horny claws and suited for
running, crawling or climbing. Limbs are paddle-like in marine turtles and
reduced in snakes.
¾ Visceral clefts never develop gills
¾ With inner and middle ear, no external ear
¾ Heart imperfectly four-chambered, two auricles and a partly divided ventricle.
¾ Internal fertilization, eggs with much yolk and protected by calcareous shell which
is made of calcium
¾ Oviparous eggs laid, or eggs retained until hatching (ovoviviparous)
¾ Poikilothermic.
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 28
Example selected : Lacerta (lizard)
Fig. 23 Lateral view of a common lizard
UB p126 fig 9.22
IV/ Class Aves (birds)
¾ Body covered with feathers.
¾ Two pairs of limbs, forelimbs modified as wings for flight; hindlimbs adapted for
perching, walking or swimming (with webs); each foot usually with four toes and
cornified skin.
¾ Visceral clefts never develop gills
¾ With inner and middle ear, no external ear
¾ Four chambered heart with two auricles and two ventricles.
¾ With delicate skeleton; mouth is a projecting beak; no teeth; very flexible neck.
¾ Respiration by lungs
¾ No urinary bladder, excrete semi-solid (uric acid). Females usually with only left
ovary and oviduct, and the sex organs only well-developed in the reproducing
season.
¾ Internal fertilisation; yolky eggs in calcareous shells, oviparous,
¾ Homoiothermic with body temperature between 40 to 45 0 C.
Example selected : Columba(pigeon)
Fig. 24 Lateral view of a pigeon.
UB p127 fig 9.23
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 29
V/ Class Mammalia
¾ Body usually with hairs; skin with many glands (sebaceous, sweat and mammary
glands)
¾ Four limbs and each with five toes; adapted for walking, running, climbing,
burrowing, swimming or flying.
¾ Visceral clefts never develop gills
¾ External, middle and inner ear, middle ear develops three ear ossicles
¾ Heart completely four-chambered (two auricles and two ventricles), red blood
cells are non-nucleated.
¾ Mouth with teeth in sockets on both jaws; tongue usually mobile; eyes with
movable lids; ears usually with external fleshy outer ear.
¾ Respiration only by lungs; a complete muscular diagram separating lungs and
heart from abdominal cavity.
¾ Brain highly developed, both cerebrum and cerebellum are large.
¾ Internal fertilisation, internal development, young are nourished by milk secreted
from mammary glands of their mother.
¾ Eggs develop within mother, (except 2 genera), viviparous, internal fertilisation
¾ Homoiothermic.
Exmaple selected : Rattus (rat)
Fig. 25 A common rat.
UB p127 fig. 9.24
The success of the mammals :
• The development of homoiothermy, accompanied by a high rate metabolism and
structures such as hair and sweat glands to control body temperature.
• Efficient organs of respiration to provide the oxygen necessary for rapid
metabolism; there are many accessory structures such as the diaphragm, the
intercostal muscles, and the separation of the blood and breathing passages.
• Viviparity, with fewer young produced, but greater parental care.
• The great development of the cerebral hemispheres allowed better
co-ordination, retention of memory and finally intelligent behaviour.
• Improved muscular co-ordination and control of posture and locomotion are
associated with the more complicated cerebellum.
• Elaboration and improvement in acuity of sight, hearing and smell.
• Heterodont dentition; a variety of teeth for a variety of purpose.
• Complete separation of blood in the heart so that the arterial blood is subjected
to a separated and stronger pressure in the systemic circulation. This had been
accompanied by the high rate of metabolism.
Buddhist Chi Hong Chi Lam Memorial College A.L. Bio. Notes (by Denise Wong)
Variety of Life and Relation of Organisms with their Environment ...... Page 30
More to Learn
Body structure :
All animals are multicellular, heterotrophic eukaryotes (the animal-like unicellular organisms are
placed in the Protoctista)
1. Colonial level = cells grouping together forming an ‘organism’ where division of labour or
differentiation of cells never occur. e.g. sponges
2. Diploblastic level = consisting of two layers of cell, an outer ectoderm and inner endoderm,
between the two layers is a non-cellular gelatinous mesogloea, and the
internal cavity is known as enteron which has only one opening. e.g.
cnidarians.
= different types of cells in the body form different tissues but they are not
organised into organs and systems.
3. Triploblastic level = this is the condition in which a third layer, called the mesoderm develops,
that separates the ectoderm from the endoderm.
(i) acoelomate
¾ they are animals the mesoderm completely fills the space between the
endoderm and ectoderm. e.g. Platyhelminthes
(ii) coelomate
¾ there is a cavity splitting the mesoderm and is filled with coelomic
fluid, which is known as the coelom. e.g annelids
¾ Function of coelom :
1. allow enlargement and development of the organs
2. the incompressible fuild is helpful in protection, support,
locomotion and transport.
3. allow independent movement of the gut and body wall.