Biology?? Help!?

Question

Describe 3 different kinds of seed dispersal.

Answer 1

1. Wind Dispersal-

i.e. the sycamore fruit has the shape of a helicopter blade so it helps to carry the heavier seeds away from the parent flower.

2.Animal Dispersal

Animals aid dispersal by either carrying the fruit or seeds on the outside of their bodies or by eating the seeds and passing them out with their droppings.
Some birds eat the fruit and then throw away the seeds.
Seeds or fruit carried on the surface of animals often have hooks to attach it to the coat of the animal.
Stickybacks and thistles are common examples.

3. Self-Dispersal

This can involve an explosion of the fruit which then throws the seeds away from the fruit.
Examples of plants that use this mechanism are the squirting cucumber and the pea plant.

4. Water Dispersal

The seeds or fruits are dropped from the plant into the rivers, lakes or seas.
They, being less dense than water, float and some of them can germinateif, on being washed up on land, the conditions are favourable

Hope this helps!

Answer 2

Seeds can be dispersed in a number of different ways. They may be carried by wind: Dandelion
water: Plants such as Pond Iris grow in or near freshwater. The seed pods break open when they ripen. Those which fall into the water float away. The seeds may be dispersed long distances in this way. They can either germinate in the water or when they become stranded on mud.
animals: a burr (constantly picking them out of my dogs hair) Some plants even shoot the seeds out explosively: Gorse is a good example of this. Sitting near Gorse bushes on a hot day in summer in Britain, can be like sitting near a firing range, as the exploding pods sound almost like gun shots. The small seeds are very effectively thrown away from the immediate area.

Answer 3

Wind dispersal (like dandelion seeds)

On animal coats (like burrs and other seeds with stickers)

Inside animals (any kind of seed that is eaten and then passes through the digestive tract).

Answer 4

manual sowing (planting)
bird pollinisation ( dropped by birds during feeding)
wind dispersal ( seeds moved by wind power to another place)

Answer 5

Gravity (including wind)
The effect of gravity on the dispersal of seeds and spores is straightforward. Heavier seeds will tend to drop downward from the parent plant, and not very far by themselves. Spores, being much lighter, are more influenced by physical movements in the environment, especially those of wind ("anemochory") and water, and therefore less strictly subject to the simple motion of gravity (see examples below). Gravity may be sufficient agent for plants growing on steep slopes, but upslope movement of a population can be a problem. The naked seeds of gymnosperms are largely dependent upon gravity for dispersal. Most extant conifers are long-lived large shrubs or tall trees, thus taking full advantage of gravitational dispersal and allowing for gradual up slope movement of a population. Dispersal of seeds strictly by gravity should not overlook storm effects: seeds from a deteriorating cone growing high on a tall, narrow tree will get spread widely during a wind storm.
Encasing seeds in a rounded fruit promotes gravity driven movement away from the parent.

Mechanical
The fruit of the squirting cucumber (Ecballium elaterium) releases its seeds in a powerful jet of liquid. The fruit of the squirting cucumber (Ecballium elaterium) releases its seeds in a powerful jet of liquid.
Numerous species have evolved mechanical means to overcome the tendency of a seed to drop close to its parent. Seedpods are often shaped so that the seeds are flung away from the parent plant with considerable force as the seedpod matures

Examples of fruit with mechanical dispersal mechanisms:
* Oxalis corniculata – capsule, as it dries, becomes sensitive to disturbance, ejecting tiny seeds in an explosive discharge.

Fluid Dispersal
Wind
For non-aquatic, terrestrial plants, the wind is an obvious supplier of energy of movement, and many plant adaptations exist that clearly take advantage of this fact. This type of seed dispersal is not efficient, but very effective. Perhaps most familiar are the feather-light fibre parachutes with attached achenes that are produced by a number of species of Asteraceae, a well-known example being the dandelion

Water
Plants that grow in water (aquatic and obligate wetland species) are likely to utilize water to disperse their seeds. For example, all mangroves disperse their offspring by water. Hydrochory is the dispersal of seeds by water; a plant which uses this method in its life cycle is termed a hydrochore. Rhizophora demonstrates an unorthodox method of propagation called vivipary: the embryo is retained on the plant until after germination; in essence, a dry seed is not produced. The hypocotyl of the germinating seedling (now called a propagule) bursts through the fruit and hangs, poised for continued growth. In R. mangle, the hypocotyl can reach a length of 20 to 25 cm; and in R. mucronata lengths up to 1 m have been recorded. Eventually, the seedling separates from the fruit, leaving its cotyledons behind, and—floating horizontally on the water surface—is carried away by tidal or river flow. After a month or two, the propagule turns vertical in the water. Once the hypocotyl of a propagule "feels" bottom or strands, roots start to develop and leaves appear at the upper end.
Adaptations commonly seen in littoral plants are those that promote flotation of the fruit, allowing the seed to be carried away on the tide or ocean currents. Examples would be:
* Cocos nucifera – the coconut produces a large, dry, fiber-filled fruit (a fibrous drupe) capable of a long survival adrift at sea.
* Calophyllum inophyllum – Alexandrian laurel or kamani produces a globose fruit that is almost cork-like.
Terrestrial plants may also have their seeds dispersed by raindrops.

By animals
A barbed seed caught in the fur of a cat.
A bumblebee disperses the pollen of Echinacea purpurea.
A significant aspect of plant-animal co-evolution involves plant adaptations that take advantage of animal abilities to locomote. Some fruit have prickly burrs or spikes that attach themselves to a passing animal's fur or feathers so that the animal will carry them away. Some seeds are contained within a soft fruit that "invites" animals to consume it. These seeds have a tough protective outer-coating so that while the fruit is digested, the seeds will pass through their host's digestive tract intact, and grow wherever they fall. Such fruit attractive to birds is perhaps the most successful of fruit adaptations related to plant dispersal. Some seeds are appealing to rodents (such as squirrels) who hoard them in hidden caches, often beneath the surface of the soil, in order to avoid starving during the winter and early spring. Those seeds that are left uneaten have the chance to germinate and grow into a new plant.
Examples of fruits with attachment hairs and structures:
* Bidens spp. – Many species of this beggartick genus produce achenes with awns that are barbed, Medicago with rolled fruits bearing thorns and spikes, many Apiaceae with spikes or spiky hairs on their fruits like Torilis, Caucalis Daucus etc,
Some animals that disperse may also eat the seed.

Answer 6

Wind is one for sure.

Answer 7

i think "human intervention" is one....