Most gymnosperms are trees. There are about 20 native gymnosperms in New Zealand, including our tallest tree, the kahikatea Dacrycarpus dacrydioides , white pine. Ferns, mosses, liverworts and green algae are all plants that have spores. Spore plants have a different life cycle. A parent plant sends out tiny spores containing special sets of chromosomes. These spores do not contain an embryo or food stores.
Fertilisation of the spores takes place away from the parent, usually in a damp place. An embryo is formed and a new plant grows from it. For more information, view the Fern life cycle interactive. New Zealand has about species of ferns and over species of moss. Classification helps us put order into the world around us. Scientists start with very big categories like plants and animals and continue to divide the groups based on shared characteristics — like methods of reproduction.
Looking at plant DNA is not the only way scientists can learn about the differences between male and female plants. For example, they can study the shape differences between male flowers and female flowers. You can do this too! Unlike humans, plants cannot move around. This means that plants need to use other strategies to move pollen to ovules to make seeds. For outcrossers, the male plants do not need to spend their energy making seeds, so they can spend more energy on making and dispersing high-quality pollen.
Similarly, since female plants do not need to make pollen, they can spend more energy on making high-quality ovules. This means that they can pass on more resources to their offspring to improve their chances of survival.
Furthermore, because dioecious plants need two different plants to reproduce, the offspring will have more variety in the genes they get from the parents. This is especially important if the environment changes, because the offspring with greater variety in their genes will be more likely to have genes that help them adapt to a new environment.
On the other hand, selfers, whose offspring only have genes from their one parent, would have less variety in their genes and might have more trouble adapting to environmental changes. This is a pretty great advantage for outcrossers! Can you think of any reasons why outcrossing might not be the best strategy for a plant to reproduce? Scientists have a couple ideas why outcrossers may not be as common as selfers. First, since male and female outcrossers need similar environments and resources to survive, they would need to compete with each other if they are too close together.
Thirty-one percent of dioecious plants avoid the issue of competition by relying on the wind to carry pollen to the female plants. While the plants are no longer competing for resources when they use the wind for pollination, the males then need to make much more pollen in order to increase the chances that their pollen reaches the distant female ovules.
You can think of this like shooting basketballs into a hoop Figure 3B. Being a selfer is a lot like shooting basketballs from right under the basketball hoop. What varied?
What functions do they have in common? What flowers would be best pollinated by a bee? Which would be best pollinated by the wind? Is one method of flower pollination more common among the flowers studied than another? Have students describe the general relationship between pollinator and flower and describe the process of pollination in detail.
Dissect plant reproductive parts. Have students prepare thin tissue samples to study under a dissecting or compound microscope. Have them draw and label what they see making sure it include the ovules in an ovary and the pollen sacs in an anther. Ask students to estimate how many seeds the flower could produce by counting the number of ovules in the ovary. Dissect a Fruit. After studying a number of different flowers, have students study fruits.
What part of the fruit was the ovary? What part of the fruit were the ovules? Compare the fruit structure of apples, berries, and peaches or other one-seeded fruits. Design a Flower. Have students work in groups to design models of flowers that are pollinated various ways.
Examples could include mimicking an insect to attract other insects, flowers shaped for hummingbirds, wind pollination, or colors and smell to attract insects and other animals. After five days, have students bring in their sheets and compare their findings. Review by asking students what they learned about pollen in their area.
The sheet can be seen in the lesson plan materials. It is amazing how life works in nature. In the same way, flowers reproduce both by growth and by the accumulation of nectar. It would be very hard to imagine a living creature existing without either a procreation process or the accumulation of nectar for sustenance. Most plants make use of both processes, but there are some that reproduce by means of somatic cells.
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