ANGIOSPERMSThe flowering plants

Spring crocus Crocus vernus

Flower structure Flowers are reproductive structures The have evolved to send and receive

pollen from one flower to another This is process of pollination Flowers are developed from a series of

modified leaves These leaves are arranged in a rings

(whorls)

Types of pollination Wind Animal Water

Bumble bee Bombus hortorum on red clover Trifolium pratense

Yorkshire fog grass Holcus lanatus

Animal pollination Usually insects Also other flying

animals e.g. hummingbirds or

fruit bats

Cerambycid beetle pollinating bramble Rubus fruticosus

Flower structure

Dog rose Rosa canina

Flower structureStigma

Style

OvaryPetal

Sepal

Filament

Anther

Pollination Pollen grains contain the

male gametes of the plant They are picked up by a

pollinator and transferred to another flower

Plants tend to specialise in pollinators

This ensures the pollen is delivered to same species of plant

Yellow archangel Lamiastrum galobdolon being pollinated by a bumble bee Bombus hortorum

Pollination

Small skipper Thymelicus flavus on marsh thistle Cirsium palustris

Pollination

The honey bee Apis melifera on marsh thistle Cirsium palustris

Pollination Some flowers are

highly specialised to encourage only one type of insect

Fox glove flowers Digitalis purpurea

Pollination Most species of flowering plants are

hermaphroditic Pollen from a flower could land on the

stigma of the same flower or another flower on the same plant = self pollination

Pollen transferred from the anther on one flower to the stigma of another flower on a different plant = cross pollination

Fertilisation Pollination ≠ Fertilisation The male gamete (the male nucleus) has

to get to the egg cell The egg cell lies in an ovule in an ovary at

the centre of the plant The pollen grain germinates on the stigma It grows a pollen tube down the style It male nuclei travel down the pollen tube

to the ovule

Fertilisation

Style

StigmaPollen grain

Ovule

Embryo sac

Pollen tubeOvary

Fertilisation

Egg cell

Polar nuclei

Embryo sac

Micropyle

Fertilisation

Pollen grains of the daisy Bellis perennis

Fertilisation

Germinating pollen grains of blue bell, Hyacinthoides non-scripta

The double fertilisation

Pollen tube

Pollen tube entering micropyle

Male nucleus + egg cell

= zygote (2n)

Male nucleus + 2 polar nuclei = endosperm nucleus (3n)

OvuleNucellus

From flower to fruit

Marsh marigold Caltha palustris

Fruits and seed dispersalAnimal dispersal Strawberry Fragaria vesca

Wind dispersal Ragwort Senecio

Explosive dispersal Bird’s foot trefoil Lotus corniculatus

Animal dispersalWood avens Geum urbanum