This is the third and final presentation of the Plants and Animals Journey. In it, students will learn about the life cycles of plants and animals.

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Previously, students explored parts and functions of plants and different categories of animals. Students will continue their study of plants and animals by learning about the life cycles of each. However, before focusing on the life cycles of plants, students will first learn about seeds, as they are an intricate part of the life cycle of many plants.

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The information in this slide introduces students to two categories of plants: those that house and produce seeds in flowers and fruits and those that produce “naked seeds.” From the slides in this set, students should realize that there are two major categories of plants: those that produce flowers and those that do not. In addition, they should understand that plants produce fruits and seeds.

Scientists refer to plants that produce seeds in flowers as flowering plants or angiosperms. Not all angiosperm flowers are the same. However, in general, a seed is produced in angiosperms when pollen from the male portion of a flower is deposited on the stigma, part of the female part of the flower. After pollination, the flower changes into a fruit that encloses single or multiple seeds. It should be noted that this information on angiosperms is provided as background information for teachers. It is not expected that students will be required to conceptualize information at this level.  

Should students ask, they may find it interesting to know that not all plants produce seeds. Ferns, mosses, and worts are the only plants that do not produce seeds. 

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Fruits from flowering plants generally fall into two categories: fleshy fruits such as cherries, apples, peaches, pears, etc., and dry fruits such as nuts, peas, and beans. The fruit aids in the dispersal of the seeds.

Students may question the purpose of fruits and other structures which house seeds. Scientists believe that fruits and cones (in pine trees and evergreen plants) may have evolved to protect seeds and aid in dispersal.

There are three main methods of seed dispersal: “hitchhiking” on animals, drifting in freshwater or the oceans, and floating in the wind. Many seeds dispersed by the wind have developed shapes and structures that help promote an extended length of travel. For example, maple trees house seeds in what is commonly referred to as “helicopters or twirlers,” structures that are similar in shape to the rotors of a helicopter. These “helicopters” are shown in the lower right corner of this slide.

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Plants that do not house seeds in flowers and therefore do not produce flowers or fruits are called gymnosperms. An example of a gymnosperm is pine trees. 

One of these most recognizable structures of gymnosperm plants is the pine cone. The seeds lie in between the individual scales of the cone. During the life cycle of the pine tree, the scales eventually open, and the seeds are dispersed from the cone.

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This slide introduces students to the life cycle of a flowering plant. As with much of nature, there are exceptions to the life cycle presented here. Ferns, mosses, and worts do not have seeds and, therefore, would have different life cycles.

In general, after viewing this and the next (Life Cycle of a Non-Flowering Plant) slides, students should understand the basic life cycle of a plant as: 

• There is an adult form of a plant.
• The adult form produces seeds.
• Seeds may be enclosed in a flower/fruit or a cone.
• Seeds are dispersed.
• Seeds germinate.
• After germination, seeds produce a seedling.
• Seedlings grow and develop into adult plants.

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This slide, Life Cycle of a Non-Flowering Plant, depicts the stages in the life cycle of a pine tree. The steps are delineated below:

• There is an adult form of a plant.
• The adult form produces seeds.
• Seeds may be enclosed in a flower/fruit or a cone.
• Seeds are dispersed.
• Seeds germinate.
• After germination, seeds produce a seedling.
• Seedlings grow and develop into adult plants.

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The Animals Life Cycles Slide Set introduces students to the life cycle of animals. Three examples are provided for students to help them understand that although many animals may look different, some of them share similar life cycles. 

The following two slides provide examples of two categories of animals – insects and amphibians, whose life cycle includes the laying of eggs. The life cycles of birds, fish, and reptiles also include eggs. The life cycles of many invertebrates also include laying eggs, but as with plants, there are exceptions and other modes of reproduction for some of these animals.

In general, after viewing this and the following slide (Frog Life Cycle), students should understand the basic life cycle of many animals as:

• • There is an adult form of an animal. 
  • The adult lays eggs.
  • From one egg comes a baby animal.
  • The baby animal undergoes metamorphosis.
  • Following metamorphosis, the baby animal undergoes several changes becoming the adult form of the animal.

In this slide of a butterfly life cycle, the adult butterfly lays eggs. One egg will hatch, becoming the caterpillar. The caterpillar will feed and then enter the next stage. Inside the chrysalis, metamorphosis takes place. An adult butterfly will emerge from the chrysalis.

Elementary students may be more familiar with the term “cocoon” than “chrysalis.” The structure shown in the image above is what most people see when viewing this stage. This structure is a chrysalis. A cocoon is an outer layer, spun by some animals, AROUND the chrysalis to protect it.

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The frog life cycle has some stages similar to that of the butterfly in that eggs develop into a structurally very different form from the eventual adult form.

• • There is an adult form of an animal. 
  • The adult lays eggs.
  • From one egg comes a baby animal.
  • The baby animal undergoes several changes becoming the adult form of the animal.

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This slide provides an example of a human (mammalian) life cycle. In general, after viewing this slide, students should understand the basic life cycle of a mammal as:

• There is an adult form of an animal. 
• The adult bears a live baby animal.
• The baby animal grows into a young animal.
• The young animal grows into an adult animal.

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The Making and Applying Connections section of the Plants and Animals Journey has been provided as a way to help students rehearse and process the information learned during the Journey as well as to become more familiar with test-taking strategies and various types of analysis questions.

Answer

Question 1: A (leaf)

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Answer

Question 2: C (frog)

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Answer

Question 3: B (flowers)

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Answer

Question 4: D (life cycles)

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