Reproduction with cones and flowers

• Alternation of generations

• Diploid sporophyte generation alternates with haploid gametophyte generation

Life Cycle of gymnosperms

• Takes place in cones, which are produced by a mature sporophyte

• Pollen cones - male – pollen grains

• Seed cones – female – ovules - which develop into a new embryo following fertilization

Structures of Flowers

• Sepals – protection during development• Petals – located inside sepals, used to

attract pollinators• Stamens – male parts consisting an anther

and filament, • filament – long stalk that supports the

anther• Anther – oval sac where meiosis takes

place

Cont.

• Carpels – innermost floral part – (pistils) where ovary produces gametophytes

• From the ovary, a stalk extends narrowing into the style, at the top is the sticky stigma

Life cycle of angiosperms

• Reproduction takes place within the flower. Following pollination and fertilization, the seed develop inside protective structure

• Pollination for most angiosperms is by animals

Fertilization

• Occurs when pollen lands on same species, pollen tube grows into style releasing two sperm nuclei

• 1 Sperm fuses with egg to produce diploid zygote, 2nd fuses with nuclei in embryo-sac which will grow into food-rich tissue called endosperm

Seed development and germination

• Angiosperm seeds mature the ovary walls thicken to form a fruit that encloses the developing seed

• Seeds dispersed by animals are typically contained in fleshy, nutritious fruits

• Wind and water require seeds that are lightweight to be carried or float

Cont.

• Dormancy – seed is alive, just not growing

• Factors like temperature and water can change dormancy

• Germination – seed absorbs water, cracking open seed coat, roots emerge and seed begins to grow

Plant Propagation

• Vegetative reproduction includes the production of new plants from horizontal stems, from plantlets, and from roots

• Plant propagation –cuttings, grafting or budding is use to make many identical copies of a plant or to produce offspring from seedless plants

Agriculture

• 10,000 to 12,000 – people began to harvest food

• Most people world wide depend on a few crops; wheat, rice, corn