PLANT LIFE CYCLES

 

 

Unit Overview

If there were no plants on Earth, there would be no life on Earth. Knowing some plant words is very important in this unit. Germination is one plant word that will help you when starting this unit. Germination is when a plant starts to grow. If you were a plant you would never need to eat because plants make all the food they need. When comparing the life cycles of plants in this unit, there will be many more plant words to learn about. Plants are producers and the most important parts of a flowering plant are the reproductive parts. Roots, stems, leaves, and flowers are parts to remember as the plant’s reproductive system. Comparing the life cycles of various plants is the focus of this unit.

 

 

VOCABULARY

observe

botanist

vascular

mature

cycle

germination

producers

perennials

repeats

visible

biennials

reproduction

 

 

The twelve vocabulary words above are used throughout unit eleven. Be prepared to know what the words mean so that you can understand how the words are used in the unit. Below are some definitions you can practice to help you understand the words better.

 

VOCABULARY DEFINITIONS

·       observe is to take notice or to watch closely

·       botanist is a person who studies plants

·       vascular denotes the system of vessels for carrying water or nutrients

·       mature is when something or someone is fully grown physically and/or mentally

·       cycle is a series of events that are regularly repeated in the same order

·       germination is when a plant begins to grow and put out shoots after a time of being dormant

·       producers is when something is made or created or grown

·       reproduction is to create or recreate a copy of something or to produce offspring

·       repeats is to do something again in the same way or the same form

·       visible is something that is seen or noticed

·       biennials are plants that grow every other year or every two years

·       perennials are plants that grow and last for a long time or more than a few years

 

The above diagram is the external anatomy of a typical flowering plant:

 

Scientists put plants into groups so they can study their life cycles. There are four basic groups of plants. These four groups are flowering seed plants, cone-bearing seed plants, ferns, and mosses. The three main differences in plants are their size, color, and texture. The main likenesses in plants are their leaves and their flowers. What scientists do when studying plants is look for patterns. These scientists are called botanists. Once botanists start to observe plants they put them into two classifications known as vascular and nonvascular. Vascular plants have tubes inside their leaves, stems, and roots. Nonvascular plants have no tubes. Nonvascular plants have fewer members in their group. Vascular plants have many members. The best way to split this group is into flowering and nonflowering plants. This unit will focus on their life cycles.

 

 

Plants grow and change just like you do. Cycles are actions that happen in the same order again and again. Your life is part of a cycle. Plants are like you in one respect they also have life cycles. Plants have a starting period, a growing period, and an ending. A good example would be any flowering plant. It grows, blooms, produces seeds, and then dies. As new seeds germinate and grow the life cycle of a flowering plant repeats. One thing to remember is that different kinds of plants have different life cycles.

 

Life Cycle of a Flowering Plant

 

 

 

 

 

(above) The "Typical" Plant Body


The Root System

·       Underground (usually)

·       Anchor the plant in the soil

·       Absorb water and nutrients

·       Conduct water and nutrients

·       Food Storage

 

 

The Shoot System

  • Above ground (usually)
  • Elevates the plant above the soil
  • Many functions including:
    • photosynthesis
    • reproduction & dispersal
    • food and water conduction

 

Note: the shoot system includes the leaves and the reproductive organs.

 

 

 

 

A tomato plant is a good example of a plant with a short life cycle. A tomato plant begins as a seed, then grows into a plant, produces small yellow flowers, and develops green fruits as the flower starts to die. When the tomato ripens its seeds mature. Once the tomato has been picked and eaten (hopefully) the summer season comes to an end. As the temperatures turn colder the tomato plant dies. If the seeds are saved and replanted the next planting season, the life cycle of the tomato will begin again. Any plant that begins as a seed, grows, and then dies during one growing season is called an annual. This means that plants that grow as an annual have a life cycle that happens yearly. This is actually a very short cycle when you think about it! Some annuals can have a life cycle as short as just a few weeks. Examples of some annuals are flowering plants like marigolds or zinnias. Some seed plants that would be annuals are beans, wheat, and corn.

Parsley is an example of a biennial plant.

Parsley is an example of a biennial plant.

A biennial plant is a flowering plant that takes two years to complete its lifecycle.

 

There are some plants that complete their life cycles in two growing seasons or two years. These plants are called biennials. It takes these plants two years for several reasons. During the first growing season, biennials not only grow but begin to change. During the first year a biennials’ roots, stems, and leaves develop. During the second year flowers, fruits, and seeds develop. After the second season the biennials die. Examples of some biennials are turnips, hollyhocks, carrots, and beets.

 

Perennials are distinct from annuals in that they return year after year.

The next group of plants to think about is quite different because of their almost permanent life cycle. Whether it is tulips or trees or daisies or lilies, the perennial group is one group of plants that lasts a long time. Roots of these plants are social. The roots and/or bulbs of perennials stay alive in the ground. The leaves may turn brown and its stems may or may not be visible. It is the perennials that have hard woody stems that loose their leaves at the end of summer. Even trees that are 1,000 years old still have a starting period, a growing period, and an end. Most trees are in their growing period and can give off seeds for any new trees to start. Whether a plant exists for a year, two years, or more than two years they each have a life cycle with a starting, growing, and ending period.

 

 

 

 

 

Below are additional educational resources and activities for this unit.

 

Unit 11 Science 140