2.2 Sexual Repro. - PLANTS Flashcards
(56 cards)
What are plants with flowers called? Where does meiosis occur in plants - what type of tissue? What is produced as a result of meiosis (haploid_____) that contain _____?
a) Angiosperms
b) Meiosis occurs in the reproductive tissue of the plant.
c) Haploid SPORES are produced as a result of meiosis which contain gametes.
What are male spores called? Where are they held? Where are they produced? What is the female spore? Where is it produced?
a) Male spores are pollen grains held in pollen sacs that are produced in the anther of the stamen.
b) The female spore is the EMBRYO SAC that is produced in the OVARY.
What does the term ‘hermaphroditic’ mean?
Different species of flowers generically differ in their ______. Despite this we can pick out 4 main features found across most species. List those 4 features (start from the outside of the flower and work your way inwards). what two things do petals range in?
a) Hermaphrodidtic refers to flowers whom have both male and female repro. organs.
b) Species differ in the APPEARANCES.
c)
1. The outermost part of the flower is the CALYX. This structure comprises of the sepals - a protective layer specifically during the bud stage where the calyx protects the flower shoot till it’s mature.
2. The next structure is the Corolla and it coprises of the petals - petals range in both size and colour. At the base of the corrolla is the nextary which produces nectar that attracts pollinators (insects) via smell & taste.
3. After this we arrive at the stamen (the male reproductive organ) which comprises of the anther (this produces the male spores) and the anther (which holds up the anther and supplies sucrose, minerals and water through its vascular tissue to the developing pollen grians.
4. The inner part of the flower is where the female reproductive organ can be found. The carpel comprises of the stigma, style & ovary.
What happens to the pollen sacs once mature? What is the stigma & what is it held up by?
The pollen sacs dehisce, opening and releasing the pollen. The stigma is the receptive surface that is held up by the style - it’s part of the carpe (female reproductive organ).
What 2 things are pollinators such as bees attracted to? What happens as the bee enters the flower? What does its thorax and legs brush against - what sticky grain does it pick up? When the bee then enters another flower , it brushes some of the other flowers sticky _____ it picked up against the ripe _____. What form of pollination has taken place? What tow forms of pollination do we discuss in biology?
a) Bees are attracted to the scent emitted from nectar that is produced from the corrolla’s nectary and they’re also attracted to large colourful petals.
b) When a bee enters the flower its thorax and legs brush against the mature anther which causes the bee to pick up stciky pollen.
c) When the bee then enters another flower it brushes some of the other flower’s sticky pollen against the RIPE stigma.
d) The description above it for CROSS pollination.
e) In biology we learn about CROSS pollinated flowers & Wind polinated flowers.
What do wind pollinated flowers NOT need that cross pollinated flowes do in order to attract what? How are their anthers structured (i.e where are they found?) - why are they found like this in wind pollinate flowers? Wind pollinated flowers have ______ stigmas that hang _____. Their stigmas have a large _____ allowing them to catch a greater proportion of what blown in the wind?
a) They do NOT need nectar as awell as large and colourful petals that are required by cross pollinated flowers in order to attract insects.
b) The anthers are found hanging outside of the flower - this is a deliberate structure because it allows the anther’s pollen to be blown away EASILY by the wind.
c) WInd pollinated flowers have FEATHERY stigmas that hang outside the flower like the anther. They have a large SA allowing them to catch a greater proportion of pollen that’s blown by the wind.
In the anther you will find pollen sacs where the diploid (2n) mother cell undergos what? What is the tapetum (it surrounds the pollen sac)? It preforms a significant role in the formation of the ______ ____, which is _____ & resistant to ______.
a) The 2n mother cells undergo meiosis.
b) The tapetum is a layer of cells that surround the pollen sac. These cells provide nutrients and regulatory molecules to the pollen sac.
c) The tapetum plays a key role in the formation of the cell wall of the pollen. The cell wall is TOUGH and resistant to chemicals.
The cell wall plays a key role in ensuring the pollen does not suffer from ____ as well as proteting the DNA inside by not allowing ____ light to ______ thorugh which can lead to DNA ____.
a) The cell wall plays a key role in protecting the pollen from dessication allowing the pollen to be transferred to another plant without drying out.
b) Furthermore, the DNA is protected by the cell wall which doesn not allow the penetration of UV light. This ensure DNA mutations do NOT arise.
Inside the pollen grain is what that undergoes what to produce 2 nuclei a) __________ & b) __________.The what produces 2 male nuclei by mitosis? What are the male gametes in a flower? What is it not?
Inside the pollen grain is a haploid nucleus who undergoes mitosis producing 2 daughter cells a) tube nucleus & b) generative nucleus. The generative nucleus undergoes mitosis to produce 2 male nuclei. The pollen grain is NOT the male gamete.
What does the ovary contain?
The ovary contains one or more ovules.
In each ovule that is found in the ovary, what is found that undergoes MEIOSIS to make 4 haploid cells? What happens to 3 of the 4 haploid cells produced? WHat happens to the remaining one haploid cell? It undergoes how many rounds of what to produce how many haploid nuclei?
In each ovary you will find a megaspore mother cell that undergoes meiosis to make 4 haploid cells. 3 of those 4 disintegrate. The remaining one cell undergoes 3 rounds of mitosis. At the end 8 haploid nuclei are formed.
Out of the 8 haploid nuclei formed one is called the what cell or _______? 2 of the 8 do what together to make a diploid nucleus called the polar nucleus? There are 3 cells collectively called what cells? There are 2 remaining cells found on either side of the 1 cell from the first part of this question.
a) Oosphere or egg cell.
b) 2 haploid cells join together to form a DIPLOID nucleus called the POLAR NUCLEUS.
c) The 3 cells are collectively called antipodal cells.
d) The last 2 cells are called the synergids.
Summarise all of the 8 cells that evolve from the 3 rounds of mitosis that occur from the haploid cell that evolved from the meiosis of the megaspore mother cell.
a) the oosphere also called the egg cell.
b) the synergids.
c) there are 2 haploid cells who FUSE together to form a diploid nucleus called the polar nucleus.
d) the last 3 cells are called the antipodal cells.
The nuclei we discussed are surrounded by what which is a layer of cells which provide what like the tapetum that is a layer of cells the surrounds the pollen sacs in the anther? There are 2 layers of cells that are called what? There is a gap between these two called the what? What type of division directly produces the female gametes that is the same with the production of the male gametes.
a) The nucellus is a layer of cells that surrounds these nuclei and provides them with nutrients.
b) The 2 layers of cells are called the integuments.
c) The gap between the two layers of cells (integuments) is called the micropyle.
d) MItosis.
Define the term pollination. Pollination brings the what (that contain the male gametes) in contact with what that is the ____ part of the flower. This contact leads to what?
a) Pollination is the TRANSFER of pollen grains from the anther to the mature stigma of a plant of the SAME species.
b) Pollination brings together the pollen grains that contain the male gametes in contact with the female parts of the flower which results in fertilisation occuring.
What is CROSS pollination? What is SELF pollination? Which is the most used form of pollination among angiosperms?
a) CROSS pollination is the transfer of pollen from the anthers of one flower to the mature stigma of another flower of the SAME species/plant type.
b) SELF pollination is the transfer of pollen from the anthers to the mature stigma of the same plant
Now we shall look at the genetic implications of cross and self pollination. Because self fertilised species inbreed they rely on 2 things for genetic variation. Think about what 2 things may bring about variation during meiosis. These species also rely on genetic ______ to take place to bring variation to their gamete’s genomes. Which type of pollination leads to more genetic variation?
a) They rely on independent assortment (a term describing the way in which different genes seperate independently of each other during meiosis) & crossing over (the exchange of DNA material between a homologous pair of chromosomes during meiosis).
b) They also rely on MUTATIONS to occur.
c) CROSS POLLINATION
If a harmful recessive allele is possessed why is this bad for a plant who self fertilises? Think about probability…
What advantage can be noted from inbreeding? Think about preservation…
a) The probability of these two harmful recessive alleles coming together increases. There’s a greater chance/likelyhood…
b) The preservation of successful genomes well suited for a particular environment.
What is outbreeding if we’ve spoken about inbreeding. It combines the what of two different individuals? Why does outbreeding lead to more genetic variation along with the independent assortment and crossing over that occurs during the development of the gametes. Why is outbreeding better than self pollination? Think about the negatives of self pollination we’ve discussed thus far.
a) Outbreeding is the combining of two gametes from different individuals.
b) It generates more genetic variation as the two gametes do not hae the same genetic make-up.
c) Outbreeding decreases the likelyhood of producing harmful allele combinations.
Going back to cross-pollination. Plants who fertilise this way must ensure that they don’t end up fertilising themselves. There are 4 methods plants can employ to ensure cross-pollination does occur. Name them. What is the difference between protandry plants and protogyny plants - which is rarer?
a) DICHOGAMY - where the stamen (the male repro. organs - anther and filament) ripen at a different time relative to the stigma of the same plant. You can have protandry & protogyny. A protandry plant’s stamens ripen BEFORE the stigma. On the other hand a protongyny plant’s stigma ripens BEFORE the anther. Protogyny plants are rarer.
b) The position of the stamen’s anther in relation to the plant’s stigma. Plants hae their anthers BELOW the stigma in order to ensure that pollen does NOT fall onto the same plant’s STIGMA.
c) Being genetically INCOMPATIBILITY - this is where pollen from a plant cannot germinate on the same plant’s stigma i.e. they’re genetically incompatible with eachother.
d) Seperation - Male and female flowers on the same plant.
DOUBLE FERTILISATION. Firstly, define fertilisation (what is it the fusion of) Fertilisation is the fusion of a female and male gamete which produces a ZYGOTE. Where is the female gamete found in flowering plants + what’s is called ? We know that the pollen grains are haploid. Their haploid nucleus divides once by mitosis to produce two daughter cells a) tube nucleus & b) the generative nucleus. We also knwo that the generative nucleus divides by mitosis to form two male HAPLOID nuclei within the pollen grain. It is these that are delivered by the POLLEN TUBE which we shall talk about shortly.
Fertilisation is the process in which a male and female gamete fuse together to form a zygote. The female gamete is found in the ovary and is called the oosphere/egg cell.
What happens when a compatible pollen grain lands on a stigma? What solution does the stigma secrete in order for _______ to occur which is subsequently followed by what?
When a compatible pollen grain lands of a stigma the sucrose solution secreted by the stigma allows for the pollen grain to germinate and produce a pollen tube.
The pollen tube nucleus is at the tip of what? Where are the two male nuclei that were produced by the generative nucleus via mitosis positioned in relation to the pollen tube nucleus?
The pollen tube nucleus is at the tip of the pollen tube and the 2 male nuclei are behind it.
Where does the pollen tube grow out from the pollen grain - what is that gap called? The pollen tube grows up a gradient of what? ___attractants. What does the pollen tube nucleus code for the production of - what enzymes & what is their function? The pollen tube grows through the gap between the 2 layers of cells called the intugements. What is that gap called? Once the pollen tube nucleus has preformed its function what happens to it?
The pollen tube grows out of the pollen grain through a gap in the cell wall known as the pit. The pollen tube grows up a gradient of chemoattractants such as GABA emitted from the ovule. The pollen tube nucleus codes for the production of hydrolase enzymes who digest the the surrounding tissues of the style allowing the pollen tube to grow. The pollen tube grows through the micropyle and then disintegrates - presumably due to having preformed its function.
