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What else can I help you with?
Why does a mechanical wave need a medium?
medium is the matter a wave trvels through
How does a kinkajou move?
it licks people if you get close
What does it mean when a air mass has been scientifically modified?
air masses do not stay in one place. they move around. it is when the exchange of heat or moisture with the surface over which an air mass trvels
Why does water travel down a string?
Water travels down a string due to capillary action, which is the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity. This occurs because water molecules are attracted to the material of the string, causing them to climb up the surface tension of the string and flow downward.
Which of these true 1 after pollination the grain trvels down inside carpel 2 all flowers are pollinated by insects 3 all flowers are pollinated by pollen from a different flower?
1. After pollination, the pollen grain travels down inside the carpel This is true : the pollen grain lands on the surface of the stigma, and germinates to give the pollen tube. The pollen tube then pushes between the looselt packed cells of the style, with the pollen tube nucleus preceding the 2 male nuclei. The pollen tube nucleus then will degenerate once the pollen tube has grown down and has penetrated the ovule, and the 2 nuclei then go on to fertilise the female gametes (one fertilises the ovum, the other fertilises the 2 female polar bodies to form the triploid endosperm which acts as a food store. Since the carpel is made up of a single leaf rolled to form an enclosed chamber : the ovary, and is effectively made up of stigma, style, ovary and ovule, i would say that it is true. 2. All flowers are pollinated by insects This is definitely false! Some flowering plants are wind pollinated. Their flowers will tend to be smaller and more inconspicuous as they have no need to attract insect, so there is no need for them to waste valuable energy amd resources making themselves pretty and coloured! Wind pollinated flowering plants include trees, cereals and grasses among others. 3. All flowers are pollinated by pollen from a different flower This is also false. Some flowering plants can self-pollinate, so the pollen shed from the anther of the flower lands directly on the stigma of the same flower, germinates, and fertilisation takes place. This is very advantageous if the plant lives in a harsh environment which is very sparsely populated, as it may not be able to reproduce otherwise, as there would need to be another plant to pollinate it. Having said that, self-pollination does have several disadvantages, and these include reduced genetic variation, and an increased likeliness of harmful recessive alleles accumulating in the offspring and causing defects etc. As a result, many plants will have mechanisms to prevent self-pollination, for example some plants are dioecious which means that the plants are unisexual - the male and female sex organs are borne on different plants, as in holly, yew and willow. Alternatively, some plants will show protogyny where the male parts of the flower mature at a different time to the female parts - this means that self-pollination cannot take place.
