Plant Life Cycles Mosses Ferns Conifers and Flowering

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 haploid Ovules 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 will mature when conditions are right • Perennial monocots typically utilize 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