Flowers are the organsresponsible for reproduction.
Four flower parts sepal petal stamen carpel
Parts of an insect pollinated flower Malestructure Female structure
Function of sepals:Protect flower when still abud; sepalMay remain, but no functiononce flower opens
Function of petals:To attract insects
Some flowers, like this pansy,have differently colored linesto: guide pollinators to the center of the flower provide a landing platform for them.
Female sex organ: Carpel Function of carpel: holds female sex cells (egg cell) Ovule Embryo sac Egg cell
Many ovules may bepresent inside one ovary Each ovule becomes a seed after fertilisation.
Stigma: Many pollen grainssticky to trap may germinate onpollen grains the stigma.
A pollen tube grows down the style to reach the micropyleMicropyleTwo malesex cells
One male gamete fertilises one egg cell
Male reproductive organ: stamenFunction of: anther: forms pollen grains filament: hold anther pollen grain: contains the male gamete
TS of anther Pollen grains
Mark with an‘X’ two placeswhere meiosis occurs. X[Meiosis occurs to produce pollen grains & egg cells]
Some trees e.g. carob, have male flowers and female flowers on SEPARATE trees Fruit only on female treesMale carob Female carobflowers flowers
Question: MAY, 2001Diagram Y shows a flower pickedfrom a holly bush. Some hollybushes are male and others arefemale.a) Was the flower shown in the diagram picked from a male or a female holly bush? Give one reason for your answer. (2)Male. Only stamens are present.
b) How can a male holly bush be distinguished from a female one, when these bushes are not in flower but in fruit? (1) Male bushes do not have fruit.
Question: MAY, 2002Some people grow Holly bushes in theirgardens simply for the beauty of theirfruit. Some Holly bushes are male andothers are female. If you decide to growHolly bushes, what must you do to makesure that you will have holly fruit in yourgarden? (2)Grow a male and a female holly bush inthe same garden.
NectariesFunction of nectaries: produce nectar at the base ofovary; in insect or bird-pollinated flowers petal sepal haired nectary at the inner base of each petal
Pollinationis the transfer of pollen grains from the anther to the stigma
CROSS-POLLINATION:the transfer of pollen grains fromthe anthers of one flower to thestigma of another flower of thesame speciesSELF-POLLINATION:the transfer of pollen grains from ananther to the stigma in the sameflower
INSECT & WIND POLLINATED FLOWERS
How can pollen be transported?By wind: By insects:Wind pollination Insect pollination
Characteristics of Insect- Pollinated flowers Large coloured petals attract insects
Characteristics of Insect Pollinated flowers Scented These flowers smell like rotten meat Carrion beetles are attracted to the rotten smell.
Characteristics of Insect- Pollinated flowers Stamens enclosed within flower Small stigma, sticky to hold pollen and enclosed within flower
Characteristics of Insect- Pollinated flowers Nectaries present
Characteristics of Insect- Pollinated flowers Pollen grains relatively heavy and large with sticky or spiny walls Pollen is less abundant than in wind-pollinated flowers
Wild oat close-up
Characteristics of Wind Pollinated flowers No scent or nectaryFlowers are small and lack bright colours
Characteristics of Wind Pollinated flowersSeveral plant families aredominated by wind-pollinated flowers, includingthe grasses.
Characteristics of Wind Pollinated flowers Wing / air sacPollen is smooth, light & small and sometimes have wing-like extensions to aid wind transport Produce of a large amount of pollen
Characteristics of Wind Pollinated flowers Stamens hanging outside flower to release pollen Anthers are large Flower hangs down The anthers as well as the flower itself hang down [sugar maple)
Stigmas hang outside flower on long stylesStigmas are feathery, giving them a large surface area to trap pollen
QuestionWhat type of pollination does this flowerhave?Give THREE ways shown by the flower thatmake it adapted for this type of pollination.
AnswerWind pollinated flower
GROWTH OFPOLLEN TUBE
Pollen tube emerges from one of the pores in wall of pollen grain pollen tubepore in wall ofpollen grain two male gametes embryo sac
Fertilisation:• is the process by which the nucleus of a male sex cell fuses with the nucleus of a female sex cell to form a single- celled zygote Fertilisation occurs ovule inside the ………..
Stages in fertilisation 2 Tip of pollen tube bursts. The male gametes enter the embryo sac. 1Two male gametes in pollen tube. 3 Fertilisation of the egg nucleus & the endosperm nucleus
Fertilisation of the endosperm nucleus: forms ENDOSPERM (oftencontains a food store used by the embryo plant) Fertilisation of the egg nucleus: ZYGOTE (forms the embryo plant)
SEED &FRUIT FORMATION
Petals, stamens, stigma & style fall off after fertilisation but the ovary begins its transformation into a fruit.
ovary develops into a fruit ovule develops into a seed
Wall of ovule develops into the seed coat [testa]
Where is food stored?
Embryo: Radicle, Plumule + Cotyledons Epicotyl: base of plumule Hypocotyl: base of radicle
External Broad bean Longitudinalappearance of with testa section of broad bean. removed. broad bean.
Label the broad bean seed cotyledons plumule radicle
Broad bean seed [learn to draw] Function of micropyle: water enters before germination Testa: a thick seed coat which protects the seed from drying up and attack by microbes
Starch in cotyledonsThe seed coat has been When a thin slice of stainedremoved from this bean cotyledon is examined underseed and several drops of the microscope, the starchiodine solution have been grains are blue in color.placed on the cotyledon.
Advantages of seed dispersal:The chance of survival is increasedbecause:1. competition between 2. new habitats may young plants is reduced be colonised
Which structure in flowering plants helps to disperse seeds?FRUIT
Question: MAY, 2006Following pollination and fertilisation,angiosperms and gymnosperms produceseeds. This is considered as a successfuladaptation of these plants.a) Give TWO advantages of production of seeds. (4)1. Seed contains a store of food for the embryo to use during germination.2. Seed can remain dormant and so survive bad conditions.3. Testa protects embryo.
b) Give ONE disadvantage of production of seeds. (2) Seeds are heavy and so difficult to be dispersed May be eaten by animals If too deep in soil, they never germinate
Four types of seed dispersal: 1. Wind dispersal 2. Animal dispersal 3. Mechanical dispersal 4. Water dispersal
1. Wind dispersal Thistle – a wing (e.g. sycamore) or – parachute (e.g. thistle)Maple seeds: Winged fruit
1. Wind dispersal – a wing or parachute allow the seed to remain airborne for a longer time and this increases its chance to be carried away some distance away from the parent plant
Pomegranate2. Animal dispersal brightly coloured, juicy, edible fruits (e.g. cherry) invites an animal to eat it Cherry Seeds within berries are often dispersed in animal faeces.
2. Animal dispersal a hooked seed (e.g. goosegrass) may drop off the animal’s coat far away from the parent plant Burdock: Spiny fruit Goosegrass: hooked fruit
2. Animal dispersal Acorns are carried by squirrels
3. Mechanical dispersal• pods of the pea family dry up in the sun and shrivel• the sides curl up, flinging out seeds
4. Water dispersal- the fruit contains air-filled walls to help it float Coconut
4. Water dispersal Coco de mer
What is the method of dispersal in each group?A: Wind A B C DB: AnimalC: WaterD: Mechanical
Question: MAY, 2006 [II A] The seeds of the Squirting Cucumber (Faqqus il-Hmir) develop in large oval fruits which when ripe, shoot out their seed on a slight disturbance. a) What type of seed dispersal is this and what is its importance? (3)
Question: MAY, 2006 [II A]i) Name TWO other methods of seed dispersal and for each name ONE type of plant that disperses its seeds using the method you mentioned. (4)Animal dispersal: burdockWind dispersal: dandelionWater dispersal: coconut dandelion
Before a seed is dispersed,water is removed from it. Why? 1. Seed is lighter. 2. Less likely to be attacked by microbes.The water content ofa seed is only about5~15% of its weight.
Seed of extinct date palm sprouts after 2,000 years [news published in 2005] The date tree that was successfullygerminated from a 2000 year old seed found in Israel.
Question: SEP, 2011Give a biological explanation for each of thefollowing statements.If a seed does not experience ideal conditionsfor germination immediately, it will not die eventhough it does not germinate. (3)The seed can remain dormant for manyyears. Being dry, microbes do not attackit. It has a food store that can be used forrespiration to keep the embryo alive.
Three conditions for seed germination1. WATER2. OXYGEN3. A SUITABLE TEMPERATURE
1. WATER for the seed to swell & burst open for the stored food to be made soluble & move to the growing embryo2. OXYGEN is needed for the embryo to respire3. A SUITABLE TEMPERATURE usually seeds won’t germinate when the temperature is below 0-5 C or above 45-50 C
What about light? most seeds will germinate in the light or dark but some germinate only in the dark others require light – one quick flash is enough A seedling
EXPERIMENTAIM: To investigate the conditions required for germination.
RESULT: Germinated No germination
CONCLUSION: Seed germination requires water, oxygen and a suitable temperature.
Question: MAY, 2004a) List the three conditions necessary for germination.b) Design an experiment that demonstrates that the three conditions listed in (a) are all necessary for germination. (7)
Two types of germination:Hypogeal:cotyledons remainbelow the ground cotyledonsEpigeal:cotyledons are pulled above theground & act as the first leaves Radicle
Hypogeal Epigealgermination e.g. germination e.g. broad bean sunflower