no clue Flashcards
Which features of life cycle, structure and physiology are common to the
protist green algae and land plants, and which are unique to land plants?
common to the protist green algae and land plants
-alternation of sporophyte and gametophyte generations
-growth arising from specialised regions called apical meristems- (more
complex in land plants than in algae)
-photosynthesis in plastids with chlorophyll a, b and carotenoids, energy
stored as starch
-requirement for light, water, mineral nutrients CO2 and oxygen
-cell walls of cellulose
unique to land plants
-an embryo arising from the union of male and female gametes that is
protected and nourished by the female gametophyte/or endosperm
-the spores produced by the sporophytes are dispersed by air, not water.
-multicellular sex organs with cellular walls that do not develop into gametes.
- meiotic and mitotic nuclear divisions in which the nuclear membrane and
nucleoli breakdown in prophase, and centrioles are only seen at meiosis in
cells that develop into motile sperm
In which major phyla of the land plants is the sporophyte larger than the
gametophyte, and in which is it smaller?
Gametophyte larger than sporophyte –phyla – Hepatophyta, Bryophyta
Sporophyte larger than gametophyte- phyla- Filicophyta, Cycadophyta,
Coniferophyta, Anthophyta
Explain why bryophytes and ferns are mainly found in moist areas
These motile sperm of these groups requires free water to swim to fertilise the
egg in the archegonium. In addition Bryophytes lack roots and usually also
cuticle.
Describe which parts of the cycad life cycle are diploid and which are haploid.
The palm-like plant with its cones is the diploid sporophyte. In the cones
inside the ovules there is a haploid female gametophyte. On male plants the
pollen is haploid. The zygote formed from fertilisation of the egg by the sperm
is diploid.
List (i) the distinguishing characteristics of angiosperms,
(i) the distinguishing characteristics of angiosperms
Flowers
Double fertilisation and endosperm
Seed enclosed in an ovary
and (ii) the
distinguishing features of monocots and eudicots.
Monocots
One cotyledon
Fibrous root system
Main leaf vein linear
Floral parts in multiples of 3
Vascular bundles of the stem scattered
No secondary xylem
eudicots
two cotyledons
tap root
leaf veins a network
floral parts in multiples of 4 or 5
vascular bundles in a ring
secondary xylem (wood)
describe the structure and function of the xylem
Xylem has parenchyma, fibres, tracheids and (in almost all flowering plants)
vessels. Water transport is in tracheids and vessels, elongated cells with walls
strengthened with cellulose and lignin. Cells are dead at maturity and in
vessels the end walls are eliminated during development. Function -water and
nutrient transport in an upward direction from roots to leaves.
describe the structure and function of phloem
Phloem consists of parenchyma, fibres, sieve tubes and companion cells. The
sieve tubes lack a nucleus at maturity but have some cytoplasm and conduct
sugars and other metabolites both upwards and downwards in strands that run
through perforated sieve plates at the ends of the cells. Companion cells
function in the loading and unloading of the sieve tubes.
explain how water and CO2 enter leaves for photosynthesis
Water uptake by roots and transport in xylem, pulled to the leaves by the
transpiration stream
CO2 through stomata (very slow diffusion through epidermis when stomata
are closed)
explain how sugars produced by photosythesis are transported throughout the plant body
sugars are transported by the phloem in the sieve tubes, movement is in excess of diffusion and explained though the pressure flow hypothesis.
Why is the terrestrial environment described as the harshest of all
environments for life?
The need for animals to have a high moisture content of cells, and to have a
moist surface across which oxygen uptake can occur makes the terrestrial
environment more ‘harsh’ than a marine or aquatic one
In what ways is the cnidarian body plan more complex than that of the
poriferans?
In contrast to poriferans, cnidarians have distinct tissues in their bodies
What special problems are presented by a parasitic lifestyle and how do
parasitic flatworms and nematodes overcome them?
-reproduction and finding new host- /reproduction may involve a motile stage
that finds a new host, and or an intermediate host that is eventually eaten by
the final host
-attachment to the lining of the host gut-/ special mouthpiece adaptations such
as the scolex in tapeworms or the piercing mouth parts in nematodes
-avoiding being digested by the host- / a resistant cuticle
- A cephalopod and a snail look very different, but they are both classified in the
Phylum Mollusca. What features are shared by cephalopods and other
molluscs? What features are unique to cephalopods amongst the molluscs?
Common features
-main body cavity a haemocoel, (not a coelom)
-formation of a mantle from outgrowths from the dorsal surface
-radula- (although cephalopods also have beaks as well)
-trochophore larva that develops into a veliger larva
Differences
-muscular foot is modified into a ring of tentacles in cephalopods
-cephalopods have a beak as well as a radula
-cephalopods have a closed circulatory system whereas gastropods and other
molluscs have an open circulatory system
The arthropods make up the great majority of animal species and in turn most
of the arthropod species are insects. From your knowledge of the biology of
insects and the other invertebrates, suggest why there are so many insect
species
- diversity of habitats/food sources drives diversity of speciation. as they can utilise a wide array of habitats and huge numbers of food rescources
- flight = enables them to exploit temporary resources, escape predators and disperse widely.
- the possibility of 2 life stages (egg and pupa) besing resistanct to environmental extremes such as heat, cold or drought enabling many habitats to be exploited
Early biologists classified cnidarians and echinoderms together in one phylum,
the Radiata, because they all had radial symmetry. On what basis are they now
placed in two distinct phyla?
Cnidarians have a very simple body structure lacking the deuterostome
development seen in the echinoderms. Echinoderms also have bilaterally
symmetrical larvae.
List the major distinguishing characteristics of (a) chordates and (b) vertebrates
Chordate characteristics:
a notochord, a ventral nerve chord, pharynx pouches
at some stage of development, an endostyle, metameric organisation and a postanal tail.
Vertebrate characteristics:
a body plan with head, trunk and post-anal tail all
supported by an endoskeleton; organ systems including a well-developed brain
and paired sense organs, a complete digestive system, an endocrine system, a
closed circulatory system and excretion by paired kidneys; a body covering with
many different adaptations and a neural crest in the embryo.
List the milestones in vertebrate evolution. How were these associated with the
movement of vertebrates from aquatic to terrestrial environments?
development of jaws/ enabled use of a much wider array of food sources
growth of legs/associated with movement on land of water,
development of the amniotic egg/ allows embryonic development within a
protective shell that still allows oxygen transfer and provides the embryo with
an ‘aquatic’ environment
respiration using lungs /internal lungs mean that the moist oxygen uptake
surface is protected from dehydration compared to exposed gills.
increases in the number of heart chambers/ enables efficient use of lungs with
separation of deoxygenated blood to be pumped to the lungs, and oxygenated
blood for circulation to tissues
