plant life cycles mosses, ferns, conifers, and flowering plants
TRANSCRIPT
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