CHAPTER 4
REVIEW QUESTIONS
4.1
The oceans provided a solution of chemicals from which organic molecules could be formed
given adequate energy input.
4.2
An atmosphere high in carbon dioxide, methane and ammonia, no oxygen or ozone layer and
thus high energy radiation from the sun and lightning.
4.3
Formation of simple organic molecules 
clumping together to form droplets of complex organic molecules 
ability of nucleic acids to replicate 
membrane separating these chemicals from their environment.
4.4
In experimental conditions, the number and types of organic compounds which can be formed
when oxygen is present is limited. Many existing bacteria are obligatory anaerobes.
4.5
A heterotrophic organism derives its nutritional requirements by taking in already formed
organic matter. It would have obtained its requirements by either absorbing organic matter
directly from the surrounding sea or by engulfing other organisms. A chemosynthetic organism
produces organic molecules using energy from the respiration of inorganic molecules. These
organisms would have taken in inorganic molecules from which to obtain the energy as well as
the simple molecules which will be converted, from their environment.
4.6
A prokaryote is a single celled organism in which there is no internal compartmentalisation of
the cell. Bacteria and cyanobacteria are living representatives of prokaryotes.
4.7
When Miller and Urey circulated methane, ammonia, water vapour and hydrogen in a container
through which they passed electric sparks they produced simple amino acids. Since that time all
known amino acids, several sugars, lipids and the bases of nucleic acids have been produced in
the laboratory under conditions proposed for ancient earth.
4.8
The cells of a prokaryote have no internal partitions (e.g. separate nucleus, mitochondria etc.)
whereas those of a eukaryote do.
4.9
The symbiotic theory of eukaryotes proposes that heterotrophic prokaryotes engulfed other
prokaryotes which survived within the prokaryote cell to become either mitochondria,
chloroplasts or other organelles.
4.10
The release of oxygen into the atmosphere, some of which became converted to ozone and
formed the ozone layer high in the earth’s atmosphere. The ozone layer reflects much of the
high energy solar radiation such as ultraviolet.
4.11
Fossils are the preserved remains of organisms, or traces of them such as footprints or exuded
chemicals.
4.12
Environmental conditions necessary for preservation are very specific (e.g. buried in a sediment
which prevents decomposition) and are not often present when or where an organism dies.
4.13
A stromatolite (stone fossil) is a rocky structure formed by the activities of certain
cyanobacteria.
4.14
A mat of cyanobacteria growing on the surface sand of shallow waters traps fine-grained
carbonate sediments. As the sediments accumulate around them, the cyanobacteria move to the
surface where they continue to trap further sediments. Metabolic reactions of the cyanobacteria
result in the conversion of the calcium carbonates to calcite that hardens the underlying
sediments. As a result dome-shaped boulders of calcite and sand form that are coated in
cyanobacteria.
4.15
Oparin suggested that the first life forms resulted from unusual activities between the
atmosphere and sea that resulted in the formation of organic molecules. By chance some of
these were able to form simple single-celled organisms that were able to self-perpetuate. One of
the early molecules that formed was chlorophyll which allowed cells to photosynthesise. The
release of oxygen from this reaction was instrumental in the formation of the ozone layer which
then prevented the entrance of high energy radiation (necessary for the conditions that allowed
the synthesis of organic molecules in the sea). Further changes to organisms resulted from
genetic mutations. The fossil record shows that the earliest life forms were simple single-celled
organisms and that changes in the types of organisms occurred over time from simple to more
complex forms.
4.16
The fossils do not give evidence for the sequence in which the various groups arose. Studies of
living organisms, showing number of tissue layers, the basic body plan, presence or absence of a
body cavity, type of embryonic development and comparison of nucleic acids provides a better
understanding of the relationships between organisms.
4.17
They are multicellular with cells specialised for different functions.
4.18
Diploblastic with no true mesoderm. Although some contractile muscle cells are present,
movement is limited. The primitive nerve net coordinating the muscle cells does not have an
overall control centre.
4.19
Dorso-ventral refers to the upper-lower body surfaces. The Platyhelminthes have an increased
number of cells but no circulatory system. The dorso-ventral flattening of the body allows rapid
exchange of respiratory gases between the cells and the environment, and of food between the
much branched gut and the cells.
4.20
Bilateral symmetry provides a leading or anterior head region. Thus sense organs in the head
allow immediate sensing of approaching stimuli. This lead to the development of a coordinating
control centre in the head.
4.21
There is no independent muscle (mesodermal origin) associated with the alimentary canal and
thus no independent movement. Food moves in the alimentary canal due to total body
movements and so there is no control of how long food remains in any particular section of the
canal.
4.22
Both are body cavities between the alimentary canal and outer body wall. Unlike the
pseudocoelom, the coelom has a muscle layer derived from mesoderm, on both sides of the
cavity (i.e. associated with the body wall and surrounding the alimentary canal).
4.23
Allowed the gut to become specialised for different functions since it could move
independently.
Allowed development of organs within the coelom.
Provided hydrostatic skeleton and thus support.
Allowed rapid diffusion of materials between inner and outer body tubes.
Allowed increase in size.
4.24
The segmented body plan is a series of initially identical units, each theoretically capable of
surviving independently. In early segmented animals, e.g. annelids, very few of these segments
are fused to perform independent functions, e.g. the head. The segments are connected together
and have common blood vessels, nerves and alimentary canal. Further fusion and modification
of the segments can occur to provide a huge variety of structural and functional adaptations, e.g.
arthropods have segments fused to form a head, thorax and abdomen. Outgrowths of the
segments can also be modified, e.g. antennae and mouthparts on the head, walking legs on the
thorax and in some cases, swimming legs on the abdomen.
4.25
Arthropoda: segments fused into head and torso; coelomic (independent movement and thus
specialisation of the alimentary canal); exoskeleton; separate legs.
4.26
Neither are segmented which allows diversification of body form.
4.27
If the skeleton is unjointed the organism must protrude in order to move (e.g. shell of the
mollusc) or must move as a whole (e.g. echinoderms), thus limiting the scope of movement both
in locomotion and in grasping or picking up food etc. A jointed skeleton allows muscles to be
attached to a solid framework across joints giving greater flexibility of movement.
4.28
SKELETON
NERVE CORD
BLOOD CIRCULATION
4.29
a.
b.
c.
ARTHROPOD
External and secreted by
ectoderm.
Double, solid, ventral.
Dorsal heart and haemocoel.
CHORDATE
Internal and formed from the
mesoderm.
Single, hollow, dorsal.
Ventral heart, closed system of
vessels.
Larval protochordates developed ability to reproduce
Storage of calcium phosphate in skin
Replacement of the notochord by jointed vertebral column enclosing the dorsal nerve cord.
Development of a cranium
Modification of the anterior gill arches.
Enlargement of the central fin bones and loss of lateral bones.
4.30
Regulation of buoyancy at different water depths.
4.31
Could be used in air breathing as an adjunct to the gills. Acted as a primitive ‘lung’.
4.32
a.
b.
c.
tetrapod – four-legged terrestrial animal.
pentadactyl – limb ending in 5 digits.
amniotic egg – an egg in which part of the zygote develops into extra-embryonic tissues,
one of which (the amnion) forms a fluid-filled sac surrounding the developing embryo.
4.33
a.
a four legged vertebrate – tetrapod literally translates as 4 legged. Only vertebrates have
this configuration.
On land – this condition evolved to allow terrestrial animals to lift the thorax off the ground
and so allow ventilation of the lungs to occur. In water this is not necessary since water is
buoyant.
Brain enclosed by a cranium; dorsal heart; single, hollow, dorsal nerve chord; bony
vertebral column of jointed and articulated vertebrae enclosing the spinal cord; breath using
lungs; pentadactyl limb.
b.
c.
4.34
Development of lobe fins
Development of swim bladder → lungs → increased surface area – double circulation
Development of pectoral and pelvic girdles to hold the body above the ground → rotation of
legs so that they move under the body
Internal fertilisation → amniotic egg → placenta
Body covering – provide insulation, decrease desiccation
fish
→
lobe fins
swim bladder
amphibia
lungs
metamorphosis
→
reptiles – amniotic egg
Dinosaurs
legs under body
Birds
endothermy
Mammals
Hair; mammary glands; internal development; jaw hinged directly to skull; middle ear from
reptilian jaw hinging bones.
4.35
A series of asteroid collisions within a relatively short time period.
Volcanic activity (which could be triggered by asteroid collisions) releasing large amounts of
carbon monoxide and sulfur gases as well as ash which could have blocked out the sunlight for
long enough to prevent photosynthesis.
Change in the Earth's magnetic field that could result in climate change.
4.36
Dinosaurs directly or indirectly depend on plants for survival. Blockage of sunlight by dust and
debris from massive asteroid impact(s) → decreased photosynthesis and heat energy →
collapse of food supplies and climate changes that added stress to starving animals.
4.37
Prototheria – egg laying; milk producing cells not grouped into mammary gland.
Metatheria – no placenta; initial development in the uterus completed attached to a teat in the
pouch.
Eutheria – placenta; full development of the embryo in the uterus.
4.38
Australia and Antarctica split off from South America prior to the evolution of the placental
mammals but after the evolution of the marsupials. Thus the only placentals in Australia flew in
(bats), came in on natural rafts (rodents), or were deliberately introduced (dingos and domestic
animals).
4.39
Any two from Table 4.3 with suitable description of the habitat and structural features.
4.40
Indigenous animals are naturally found in a particular area, e.g. koalas in Australia.
Exotic animals have been imported from another country, e.g. sheep in Australia.
Feral animals are exotics that have escaped captivity and successfully live in the wild, e.g.
rabbits, foxes and buffalo in Australia.
4.41
The adaptations are probably related to the transition from water to land, e.g. the water and
dissolved nutrients are in the ground, thus roots are specialised for seeking and absorbing these
as well as to anchor the plant in position. Since these parts are underground they cannot
photosynthesise and thus food must be transported to them. Stems are strengthened structures to
overcome the lack of buoyancy of the air and to display the leaves effectively for
photosynthesis.
4.42
A sexually reproducing generation produces offspring that reproduce asexually. Their offspring
become the next sexually reproducing generation.
4.43
The diploid sporophyte generation produces spores asexually by meiosis, whilst the haploid
gametophyte generation produces gametes by mitosis, which unite to form the next sporophyte
generation in a process of sexual reproduction.
4.44
A sexually reproducing stage allows variation of characteristics. Those individuals with
characteristics which give the plant in an advantage in its environment produce more offspring
which transmit this information through to the next generation during asexual reproduction.
4.45
In mitosis, the cells produced are exactly the same as the ‘parent’ cell (with the same number
and types of chromosomes). In meiosis, the daughter cells have the same types of chromosomes
but only half the number.
4.46
Growth of the plant by mitosis ensures that all of the cells of the plant have the same
information in their nucleus.
4.47
Both green algae and plants:
 Have photosynthetic pigments chlorophyll a and b found in membranous stacks in
chloroplasts.
 Have cellulose cell walls.
 Store energy as starch.
4.48
Both
 Exhibit delayed meiosis and the formation of a diploid sporophyte generation.
 Have similar proportions of cellulose in their cell walls.
 Have similar mechanisms of cell division.
 Have similar nuclear genes and RNA.
4.49
Normally the adult alga is haploid and zygotes are diploid. These undergo meiosis before
growing by mitotic division into the new adult. In delayed meiosis, the diploid zygote grows by
mitotic division to form an asexually reproducing diploid individual that produces spores by
meiosis, i.e. a sporophyte generation. This allows amplification of the number of spores that can
be produced by a single zygote – an adaptation to terrestrial existence.
4.50
The stalk and capsule of the moss comprise the sporophyte generation which is formed by
sexual reproduction. Since the male gametes must swim in a film of water to the female gamete,
sexual reproduction can only occur when the surface of the moss plant is wet. Thus the
sporophyte will only be seen after a period of rain.
4.51
The gametophyte of the moss is the dominant phase and provides nourishment for the
sporophyte which remains embedded in the female tissues. The gametophyte of the fern, whilst
still photosynthetic, is a temporary structure that disintegrates once the sporophyte is
established. In both plants the gametophyte produces either male or female gametes by mitosis.
The female gamete remains within the archegonium and the male swims to it. Fertilisation and
development is internal.
4.52
In seed production, both male and female spores germinate within the tissues of the sporophyte
plant (male forms the pollen grain and female the embryo sac). This necessitated the prior
evolution of separate male and female spores.
4.53
Pollen has a waxy protective coating resistant to environmental stresses (dehydration and
temperature change) as it is transferred to the same or a different plant.
Fertilisation does not require an external source of water.
The seed is small enough to be transported by air, water or an animal to a new area for
germination.
The embryo has its own food source.
The seed coat protects the embryo until conditions are suitable for germination.
4.54
Secondary growth is the increase in girth of the plant as a result of the development of new
vascular tissue and bark. The old phloem and bark shed by the xylem is maintained.
4.55
As the plant grows taller it needs a stronger support structure, which is attained through
secondary growth. The old xylem cells become non-functional in transport and become filled
with the plant’s waste products, which gives them the strength to support the plant.
4.56
The gametophyte generation in the seed plants is even more reduced than in the ferns: the
female remains as part of the structure of the sporophyte and the male is the pollen grain which
is transported, generally without water, to the female plant. Thus an external source of water is
not required for fertilisation to occur.
4.57
Pollen is the male gametophyte.
Seed is the structure enclosing the embryonic plant and food reserve and is surrounded by a
protective coat.
Fruit is the expanded ovary wall enclosing the seeds.