Allelochemicals, possible roles in the life of the
plant
1/ storage of unwanted products. 2/plant structure - cell
walls. 3/plant colour and smell. 4/defence against physical factors e.g. cold,
salinity, UV light. 5/defence against herbivores. |
Essential features of the theory of island biogeography
a)number of species increases with increase in island area. b)for
an island of a given size number of species decreases with distance from source
area. c)continual turnover of species where colonizations are balanced by
extinctions. |
Advantages of dispersal in
plants
1) Reduces chance of offspring/sibling/parent competition. 2)
Reduces inbreeding. 3) Increases chance of finding "safe" site. |
Types of competition
Intraspecific
competition i.e. competition between individuals of same species. Exploitation
competition makes resources e.g. food unavailable to others. Interference
competition occupying space, defending territory preventing others reaching
resource. Interspecific competition i.e. competition between different species. |
Characteristics of pioneer plant
species
1)Abundant in soil seed bank. 2) Small seeds. 3) Shade
intolerant. Germination only in open sites. Dormancy broken or germination
enhanced by high light intensity, high R/FR ratio light, fluctuating or high
temp. and/or moisture, high NO3 4) Rapid growth. 5) Early
reproduction. 6) Large investment of resources in reproduction (r-selected). 7)
Reproduction continuous or frequent. 8) Mechanisms for distant seed dispersal
(birds, insects, wind). 9)Short lived. 10)Genetically diverse. 11)
Phenotypically plastic. 12) Low density wood, in trees. 13) Leaves not robust
and short lived. |
Differences between the flora and fauna
of continental and oceanic islands .
Continental islands usually
have more species for their size
Continental islands usually have a subset of mainland species;
oceanic islands have a subset of those that are good at dispersal
Oceanic islands contain a greater
number of endemic species.
Oceanic
islands rarely have freshwater fish.
Oceanic island species often lose their powers of
dispersal.
Oceanic island species may
differ remarkable in size from mainland species. |
Nutrition from plant parts for
herbivores
(a) nitrogen - young leaves, seeds, nectar and some
pollen (b) carbohydrate - phloem and nectar, wood (structural carbohydrates) |
three species which exhibit population cycles
1) Lynx, 10 years 2)
Red grouse, 4-6 years 3) Larch budmoth, 8-10 years. |
Plant animal interactions. Illustrate the main benefits
plants receive from interacting with animals.
Dispersal by attachment,
frugivory and granivory. Pollination, thereby increasing genetic variation and
fitness. |
Interspecific competition. List the criteria which
should be satisfied to demonstrate its occurrence.
Both species
must have a common resource e.g., food. There must be intraspecific competition
between individuals of the same species. The performance of each species should
be better when they are separate than when they are together. Removal of one
species should increase the performance of the remaining species. The addition
of the common resource should increase the performance of both species, thereby
showing it is the limiting factor. |
Plant apparancy. List features of plants which
contribute to their apparency to insects.
Geographical extent, length
of presence, common abundance, predictable and perennial, length of time
available, no. of niches, island size. |
Soil condition. List 3 differences in soil conditions
between young mobile sand dunes and old fixed sand dunes.
Low organic
content in young, higher in old. Higher pH in young, lower in old. High mineral
content in young, lower in old. |
Roles of plant secondary compounds
1. storage of
unwanted products 2. structural support e.g. cell walls, lignin 3. plant colour
and smell 4. defence against cold, salinity, UV light 5. defence against
herbivores e.g. alkaloids |
Social insects - 3 major traits.
1.Individuals of the same species co-operate in caring for the young.
2. There is a reproductive division of labour.
3. There is an overlap of at least 2 generations in life stages capable of contributing to colony behaviour. |
features of the major evolutionary trends in
pollination
(a) Specialization: Low pollen/ovule ration, economic
and efficient, environmentally sensitive. (b) Reduction of pollen, fusion of
parts, enclosure of nectar, special odours. Wind: High pollen/ovule ratio,
independent of animals, but very wasteful of pollen and plants. (c) Reduction
of floral parts, separation of sexes, loss of nectar. (d) Non-specialization:
intermediate pollen/ovule ratio, buffered against environmental disturbances. |
Reproductive barriers between species
1. Ecological isolation. Populations live in different habitats and do not meet.
2. Temporal isolation. Mating or flowering occur at different seasons or times of the day.
3. Behavioural isolation. Males and females of the different species are not attracted to each other.
4. Mechanical isolation. Structural differences in genitalia or flower prevent copulation or pollen transfer.
5. Gametic isolation. Female and male gametes fail to attract each other, or are inviable.
6. Hybrid inviability. Hybrid zygotes fail to develop, of fail to reach sexual maturity.
7. Hybrid sterility. Hybrids fail to produce functional gametes.
8. Hybrid breakdown. The offspring of hybrids have reduced viability or fertility. |
3 main trends in pollination mechanisms which can be observed in flowering plants, plus examples
1
specialization, e.g. odours, reduction of pollen, fusion of parts, enclosure of
nectar, e.g., hammer orchid, yucca
2
wind, e.g., reduction of floral parts, loss of nectar, separation of sexes,
e.g. festuca rubra
3
non-specialisation, e.g.- formation of groups of flowers with more or less
exposed nectar, e.g., bellis perennis |
The main parts of a flowering plant and their function.
Flower. Generation and reproduction. Can be hermaphrodite or bisexual, producing the pollen grain or containing the ovule, or both. Female and bisexual flowers produce the seed when they are fertilised.
Stem. Carries solutes from roots to leaves. Carries flood from leaves to other parts of the plant. Bears the leaves in a position for photosynthesis. Displays the flower for pollination. Exposes the seeds for dispersal.
Leaf. Respiration - taking in oxygen and giving out carbon dioxide and water. Transpiration - giving off excess water in the for of vapour. Photosynthesis - making food from light.
Roots. Anchor the plant to the substrate. Absorb inorganic salts in solution. Transports nutrients to leaves. |
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