Introduction to Plants

Five Plant Characteristics   Plants are multicellular eukaryotes.   Plants are autotrophs containing chloroplasts for photosynthesis.   Plants are non-motile (fixed to one spot).   Plants cell walls are made of cellulose.   Plants respond to the environment.

The First Plants  The earliest photosynthetic organisms were plant-like protists that lived in water.  Even today about 70% of photosynthesis occurs in the oceans.

Plant Adaptations to Land The major adaptations to life on land included: 1. Protection from drying out for leaves and stems. 2. A system of vessels to transport water, nutrients and wastes in the roots, stems and leaves. 3. The use of stems and leaves as a system to hold the plant up and capture energy from light.

Non-vascular Plants  The earliest land plants were non-vascular.  Non-vascular plants have no system of vessels to carry nutrients, water or waste.  These mosses, liverworts, and hornworts evolved about 500 mya from green algae.

Non-vascular Plant Reproduction  They need a moist surface for gametes to swim together for reproduction.  Make spores not seeds.  Non-vascular plants lack true leaves, roots or stems and are small.  All water, nutrients and waste move between cells by osmosis and diffusion. Their growth is limited.

Vascular Plants - Ferns  As plants adapted to land they evolved more complex structures.  Ferns were the first vascular plants.  Ferns have vascular tissue or vessels that transport materials between different parts of the plant so they can grow taller.

 Ferns have true roots to anchor them and absorb water and minerals.  Fern leaves are photosynthetic and absorb gases from the atmosphere.  Ferns still use spores for reproduction.

Plants with Seeds  Next plants evolved seeds, an evolutionary adaptation to improve reproductive success.  Seeds allow a plant to reproduce sexually without needing water for the gametes to swim to each other.  Seeds contain a fully developed embryo, a food supply and a water-proof seed coat.

Gymnosperms  Gymnosperms are plants that produce “naked seeds”.  Gymnosperms include all the conifers or pine trees that produce cones.

Angiosperms  The most recent evolutionary adaptation for plants was to produce flowers, again to improve reproductive success.  Angiosperms are flowering plants. The seeds of angiosperms are protected in the fruit and attract animals to distribute the seeds.

Parts of a Flower One pollen fertilizes each seed or ovule. Pollen also fertilizes the ovary which develops into the fruit surrounding and protecting the seeds.

Monocots and Dicots  There are two classes of angiosperms - monocots and dicots.  Monocots have one seed leaf and dicots have two seed leaves.  There are numerous differences between monocots and dicots that you will learn about in this unit.

Can you remember the missing labels?

And these missing labels?