Plant Reproduction Flashcards
What are all the parts of a dicotyledonous insect-pollinated flower?
receptacle, calyx, sepal, corolla, petal
stamen (male parts): anther and filament
carpel (female parts): stigma, style, ovary and ovule
What is the function of a sepal?
they protect the flower when it is in a bud
What is the calyx?
Outermost ring of structures, collective term for all of the sepals
What is the corolla?
A ring of petals (collective name)
- may be a nectary at the base (releasing nectars to attract pollinators)
What is the function of a petal?
Colourful to attract insects
- the inner sterile whorl of a flower
What is the function of the anther?
where pollen is produced
- consists of 4 pollen sacs that split and release pollen
What is the function of the filament?
vascular tissue that supports the anther
- transports food materials needed for formation of pollen grains
What is the function of the stigma?
sticky part that receives pollen from the anther
What is the function of the style?
pollen grows a tube down the style to the ovule
What is the function of the ovary?
Fertile part of the carpel, meiosis occurs here to produce haploid ovules
What is the function of the ovule?
contains an egg that after fertilisation forms the seed
What is the function of the stamen?
male part of the flower, consisting of the anther and the filament
What is the function of the carpel?
female part of the flower, consisting of the stigma, style, ovary and ovule
Insect-pollinated flower vs wind-pollinated: pollen
insect: produces small quantities of sticky, sculptured pollen, larger pollen grains (less wastage of pollen)
wind: produces large quantities of smooth, small pollen (most pollen doesn’t reach another flower)
Insect-pollinated flower vs wind-pollinated: anther and stigma
insect: both within the flower, anther positioned to rub pollen onto the back of insects (e.g. bees)
wind: hang outside the flower so they can be exposed to wind (wind carry pollen away), feathery to increase SA for catching pollen
Insect-pollinated flower vs wind-pollinated: petals
insect: colourful petals to attract insects
wind: absent
Insect-pollinated flower vs wind-pollinated: nectar
insect: usually contain nectar (sucrose)
wind: no nectar
Insect-pollinated flower vs wind-pollinated: scent
insect: produce a scent
wind: no scent
Insect-pollinated flower vs wind-pollinated: attracting insects
insect: attracts
wind: no need to attract insects
What are the 2 distinct phases of the life cycle in flowering plants?
the diploid sporophyte
- the haploid gametophyte
What is the diploid sporophyte phase?
Produces haploid spores by meiosis
- spores develop into haploid gametophyte, which produces haploid gametes by meiosis
What is self-pollination?
The pollen from the anthers of a flower is transferred to the mature stigma of the same flower or another flower of the same plant
What is cross-pollination?
Pollen is transferred from the anthers of one flower to the mature stigma of another flower on another plant of the same species
What are the advantages of self-pollination?
diversity only arises from independent assortment and crossing over
suited to stable environments
preserves genes well suited to that environment
What are the advantages to cross-pollination?
prevents inbreeding (form of outbreeding)
harmful recessive alleles less likely to be expressed
allows species to survive in a changing environment (can withstand environmental change)
How do flowers prevent self-pollination?
stigma is above the stamen (pollen can’t fall onto it)
stigma and anther mature at different times (protandry or protogyny)
separate male and female plants (dioecious)
What is pollination?
The transfer of pollen grains from anther to the mature stigma of a plant of the same species
What are the labels of the cross section of an anther?
Pollen sac
filament (contains vascular bundle)
epidermis
fibrous layer
tapetum
pollen
Describe the cross section of the anther?
cross section of anther shows 4 chambers called pollen sacs
each pollen sac is enclosed by a protective epidermis and fibrous layer
inside the fibrous layer is the tapetum (food store providing energy for cell divisions)
What happens when the pollen has matured?
The anther dries out, splits open at the weakest part/stomium, this exposes the pollen grains
This process is called dehiscence
What is dehiscence?
The opening of the anther, releasing pollen grains