Plant Life Cycles

Mosses, Ferns, Conifers, and

Flowering Plants

General Life Cycle of Plants

• Recall that all plants cycle between two phases during their life

• Called ‘alternation of generations’

• The two generations are gametophytes and sporophytes

Life Cycles of Seed Plants

• Seed plants evolved after mosses and ferns

• They have efficient vascular systems and seeds to nourish offspring

• Gymnosperms = mostly pine trees; use cones for reproduction

• Angiosperms = flowering plants; use flowers to attract pollinators

Gymnosperm Life Cycle

• In pine trees, the mature tree is the sporophyte (diploid)

• The tree makes two cone types: the male pollen cone and female seed cone

• Pollen cones make the male gametophyte: pollen

Gymnosperm Life Cycle

• The seed cone produces the female gametophyte, which produces thousands of eggs

• At the base of each cone scale,

there are two ovules where the

gametophyte develops• The gametophyte

and pollen are

haploidOvules developing gametophytes

Gymnosperm Life Cycle

• Wind carries pollen to the female cones, where fertilization occurs

• Fertilization creates a young, diploid sporophyte on the cone scale

• Once the cone drops, the sporophyte develops into a mature plant

Angiosperm Life Cycle

• In flowering plants, the sporophyte is the mature plant we see

• The sporophyte produces flowers, complete with anthers and an ovary

• Anthers create pollen, the male gametophyte

Angiosperm Life Cycle

• The female gametophyte develops in the ovule (eggs) of the flower

• Pollen lands on the stigma, travels down the style, and fertilizes the ovule

• The fertilized egg is now diploid, and is packaged into a seed

• The seed is surrounded by a fleshy ovary called ‘fruit’

Angiosperm Life Cycle

• When the fruit falls to the ground, the seed can grow into a seedling, a new, diploid sporophyte

Fruit Development

• Once fertilization occurs, flower petals die off and nutrients are rushed to the seed

• Parts of the ovule toughen to form a seed coat

• The ovary containing the ovules forms a tough skin and swells with sugary tissue

• Fruit = a seed enclosed in an ovary

Types of Fruit

• Simple fruit = development of large ovary from one pistil

• Aggregate fruit = development of small ovaries from multiple pistils on one flower

• Multiple fruit = development of ovaries from many flowers that fuse together to form one mass

Aggregate Fruits

Simple Fruits

Multiple Fruits

What’s a Bulb?

• A bulb is NOT a fruit or seed• A bulb is an entire plant, resting dormant

underground• Bulbs contain precursors to root,shoot, and leaf systems that willmature when conditions are right• Perennial monocots typicallyutilize bulbs

Life Cycles Review!

• Complete the Coloring Activity for Gymnosperm and Angiosperms

• As a class, we will go outside and collect one piece of evidence of each life cycle (moss, fern, gymnosperm, angiosperm)

• Inside, you will identify the pieces of evidence and explain all four life cycles to a partner