Biology 2014-2015

Introduction to Plants
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Section 22-1 

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22-1 Introduction to Plants

    plants dominate the landscape

    plants provide the base for food chains on land

    plants provide shelter, shade and oxygen for animals

    oldest fossiI evidence dates from about 470 million years ago

 

What is a Plant?

    Plants are members of the kingdom Plantae

    Multicellular eukaryotes with cell walls made of cellulose

    Carry out photosynthesis using the green pigments chlorophyll a and b

    Autotrophic, do not gather food, move about or directly struggle with predators

 

The Plant Life Cycle

    Plants life cycles have alternation of generations

v    Gametophyte (N) or haploid, gamete-producing plant

v    Sporophyte (2N) or diploid, spore-producing plant

v    Gametes = egg & sperm (haploid cells) when fuse produce a new diploid individual

v    Spores are reproductive cells that produce a new individual by mitosis

v    Plants must be able to reproduce in dry environments where there is no water through which gametes move from plants to plant

 

What Plants Need To Survive

 

1.  Sunlight

w   Use energy from the sun to carry out photosynthesis

w   Photosynthetic organs such as leaves are broad and flat to maximize light absorption

 

2.  Water and Minerals

w   All cells require a constant supply of water

w   Water is a raw material of photosynthesis and is used up quickly when the sun is shining

w   Plants have developed structures that limit water loss

w   Minerals that plants absorb with water are nutrients needed for growth

 

3.  Gas Exchange

w   Plants need oxygen to support respiration and carbon dioxide to carry out photosynthesis

w   Gas exchange takes place with the atmosphere without losing excessive water

 

4.  Movement of Water and Nutrients

w   plants take up water and minerals through their roots

w   food is made in their leaves

w   plants have specialized tissues that carry the water and distribute the food throughout the plant body

 

Early Plants

 

Origins in the Water

    first green plants evolved from an organism much like the multicellular green algae living today

    algae have similar reproductive cycles to those of plants

    green algae have cell walls and photosynthetic pigments identical to those in plants

 

The First Plants

    The first true plants were still dependent on water to complete their life cycles

    Early plants were similar to today's mosses in that they were simple and grew close to the ground

    They were common in damp swampy regions

    From these first plants others began to evolve:

v    mosses and their relatives

v    ferns

v    cone-bearing plants

v    flowering plants

 

Overview of the Plant Kingdom

    Botanists divide the plant kingdom into four groups based on three important features:

        water-conducting tissues

        seeds

        flowers

    Today, plant scientists classify plants by their DNA sequences

    Since 1994, the project known as "Deep Green" has provided evidence that first plants evolved from fresh water green algae instead of from the sea as had been thought