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Unit 2 Seed dispersal How do seeds move from place to place?

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1 Unit 2 Seed dispersal How do seeds move from place to place?
Seed dispersal: Unit 2

2 Where do ducks carry seeds?
Externally (feet, feathers, beak). Some children may also add internal retention at this stage but use slide 13 for APP after the visit and work on how seeds travel. Seed dispersal: Unit 2

3 Gravity Acorns: • How far do they fall from the
tree • Mammals and birds bury acorns to eat in the winter. What happens to the ones left in the ground? Listen – how long does it take to fall? Rate: 32ft per second per second. What sort of trees will grow if the squirrel/jay dies? If they have buried seeds they prefer to eat (highly nutritious), the seeds that are buried and germinate will be suitable for others in their species and potentially influence future survival rate. Darwin’s ways of working: Unit 1 Seed dispersal: Unit 2

4 Wind Dandelion (Taraxacum officinale) • What helps the seed to move?
“beautifully plumed seed” Charles Darwin, On the Origin of Species, 1859 • Can you think of other ways that make seeds light enough to be blown on the wind? How do you make the structure very light? Smaller seed; bigger area of light tissue that can remain airborne in the slightest up draught. Darwin’s ways of working: Unit 1 Seed dispersal: Unit 2

5 Gravity and wind Sycamore (Acer pseudoplatanus)
• How tall is a fully grown Sycamore tree? • Does each seed fall straight down? acer-pseudoplatanus/video- 09b.html Hint: look at the wooden telegraph pole – how tall is a pole (approximately 7.5 metres although they do vary) Using the image of the sycamore - was the wind blowing on that day? (branches not twisting and sky blue). What time of year was the image taken? (summer?) Seeds twirl downwards – height and wind speed determine how far they will travel. Seed dispersal: Unit 2

6 Pepper Pot (sways on the stalk)
Common Poppy (Papaver rhoeas) • Where does the seed come out? • About how tall is a poppy flower? • What could cause the stalk to sway? • Why do you think each poppy plant can produce around 17,000 seeds? Holes in the top of the seed capsule Height from 20cm to 60cm Wind, brushed by animals. Superfecundity; only one seed needs to germinate but the conditions may not be suitable so many are produced. Suitable = soil, temperature, rainfall, light levels, moulds, diseases, eaten by animals, (now also human interventions). Seed dispersal: Unit 2

7 Animals - eating Blackberry (Rubus fruticosus)
• Which of these berries do you think will be eaten first? • What happens to the seed after the fruit has been eaten? Potential to revise growth and pollination; which flower was available to pollinate first? Why so many – see slide 6. Number of sections - differentiate – 8, 9, 11, 12, 13 Blackberry seed is not damaged in its passage through an animal’s digestive system. Seed emerge intact, the pulp having been digested, and with it is a small amount of fertiliser (guano). Count the number of blackberries on this branch. Each one will have about 10 sections each with a seed. How many seeds are on this one branch? Seed dispersal: Unit 2

8 Animals - clinging Cleavers (Galium aparine)
• How do you think the fruits of cleavers move around? • Which wild animals could do this? Show the image after children have given their ideas (compare with Velcro). Image of Merry the Springer Spaniel covered in cleavers. Ask which wild animals could move seeds around. Seed dispersal: Unit 2

9 Water Marsh marigold (Caltha palustris) • Where do they live?
• What do you think will happen to the seeds when they fall out of the pod? marsh-marigold/caltha-palustris/ image-A16924.html Next to water; pond, rivers, bogs, marshes. The seed floats – can be eaten by water dwelling/visiting animals. Seed dispersal: Unit 2

10 Explosive - springing apart
Sweet pea seed (Lathyrus odoratus) When will the seed pod be dry enough to suddenly explode and twist? • Why do the seeds spray away from the Plant? • How far can these seeds travel? Seeds burst in hot dry weather (late summer?). Where they drop – how far they travel is important. Seeds can drop near parent plants and take advantage of suitable soil but compete for light, nutrients, water. Moving further away they risk competition with other plants (including parent plants). Competition is an important factor in seeds germination, growth to maturity and seed production. Seed dispersal: Unit 2

11 Explosive - pushing forward
Squirting cucumber (Ecballium elaterium) These plants live in hot dry countries. When drops of rain hit the ripe fruit they push off the plant squirting their seeds behind them. • Why is rain a helpful trigger? Hint – it needs water to grow. You may want to buy the BBC video Private life of plants 1. Travelling (Part 2/5) if you want to show the time lapse film of the squirting action. Alternatively read the description and children draw a picture of the squirting cucumber as it pushes away from the plant and squirts seed behind (this is a learning skills for science [LSS] activity) Seed dispersal: Unit 2

12 Here Darwin collected mud with lots of seeds in it
Keston Ponds Here Darwin collected mud with lots of seeds in it Which trees or water plants can be seen – oak trees and water plants (floating on water) Seed dispersal: Unit 2

13 A duck inside and outside
The seeds noted in slide 12 fall into the water and onto the bank. How could they be transported by a duck? Discuss the digestive tract and how long the seed stays in it (see Teachers’ notes) Seed dispersal: Unit 2


15 Seed dispersal: Unit 2

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