AngiospermsAngiosperms

Angiosperms Flowering Plants

All species produce a flower of some type

Use insects, animals and wind for pollination

Largest group of plants on Earth 250 000 species

Angiosperm Seeds Vary in size

e.g. coconut to banana!

Often enclosed usually in a fruit.

Can remain dormant for long periods of time until environmental conditions are right for germination

Often spread using animals or insects

This is the most successful group of plants. Turn and talk…..Why???

Enclosed seed protects seed in early development

Flower/Fruit Encourages pollination and seed dispersal by insects

or animals Angiosperms evolved along with insects

Angiosperm Seeds

Angiosperm Groups Arranged in two

groups: Monocotyledons

“Monocots”

Dicotyledons “Dicots”

Fig 29.1 in text

Cotyledon = seed leaf First leaf to appear

Monocots – Key features Embryo

one cotyledon

Root Vascular tissue forms a ring

Stem Vascular tissue scattered

Monocots – Key features Leaves

Leaves have parallel veins.

Flower parts are in multiples of three.

Embryo Two cotyledons

Root Vascular tissue forms a cross

Stem Vascular tissue arranged in a ring

Dicots – Key Features

Leaves Leaves have ‘net-like’ veins.

Flower Parts in multiples of four or five.

Dicots – Key Features

Monocot or Dicot?

Plant Structure 2 Main Systems

Root system Functions: Water and mineral absorption,

anchorage and support, carbohydrate storage, production of hormones

Main Organs: Roots

Shoot system Functions: Photosynthesis, gas exchange,

reproduction Main organs: Stems, Leaves, Flowers/Fruits

Structure cont’d Systems connected by vascular tissue

Tissues for the transport of materials throughout the plant body.

Xylem Conduct water and minerals from roots to leaves Dead at maturity

Phloem Conducts glucose from the leaves to rest of the plant Alive at maturity

Reproduction: Flowers Flowers

Sexual reproductive structure In alternation of generations, still a diploid structure

Is it a girl or a boy? Male

produce the mobile gametes Females

produce the non-mobile gametes

Reproduction Flowers cont’d

Dioecious male and female reproductive organs are

carried on separate individual plants of the same species.

Monoecious have both male and female reproductive

organs borne on a single plant.

Reproduction Flowers cont’d

– Male Reproductive Organs

– Stamen Anther

contains tissue that gives rise to pollen grains

Filament Pollen

Male gamete

Reproduction Flowers cont’d Female Reproductive Organs

Carpel Stigma

Style

Ovary hollow area that encloses one or

more ovules. Ovule

contains an embryo sac, the structure that gives rise to the female gamete, the egg.

In most flowers, the carpels are fused together to form a pistil.

Flower Structure (Fig. 29.16)

Receptacle base of the flower specialized region of

the stem

Calyx consisting of a ring of

sepals Can be many colours

or small green and leaf-like

Flower Structure (Fig. 29.16) cont’d

Corolla composed of petals primary function of

attracting insects to serve as pollinators

Stamen

Carpel

Angiosperm Lifecycle

Fig. 29.17

Angiosperm Lifecycle cont’d Anther

Many mother cells divide by meiosis to create haploid microspores

Called Pollen

Each grain of pollen contains two haploid nuclei

Angiosperm Lifecycle cont’d Ovule

Mother cell divides by meiosis to form 4 haploid megaspores

Only one megaspore develops into an egg in each ovule.

Ovule also contains a diploid nucleus

Angiosperm Lifecycle cont’d

Pollination Transfer of pollen from anther to stigma

Pollen attaches to the stigma, and travels down the style to the ovary

Self – fertilization is possible in plants Doesn’t increase genetic variability, so often the

stigma is not ‘ready’ at the same time as the pollen

Angiosperm Lifecycle cont’d Fertilization

Pollen has two haploid nuclei

Angiosperms exhibit double fertilization

Fertilization 1 Fusion of microspore and egg Produces diploid zygote

Fertilization 2 Fusion of microspore and a diploid cell Produces endosperm

Has 3 sets of chromosomes = triploid (3N) Nutritive tissue of seed

Angiosperm Lifecycle cont’d

Seed Development Zygote embryo

Endosperm nutritive tissue

Ovule mature seed.

Ovary fruit.

Seed dispersal mechanisms Hooks and spines

Attach to and are carried by animals.

Explosion Throws seeds from parent

Wind Lightweight seeds, parachutelike or winglike

structures

Seed dispersal mechanisms cont’d

Water Seeds contain air pockets to allow them to

float.

Fleshy fruits Nutritious for animals Pass unharmed through the digestive system

and are deposited in the animal’s waste (ideal fertilizer)