University of California, Los Angeles - LS 7B

11/19/2020

Photosynthetic World

Part1)Why do you think this somewhat interesting life cycle is so universal? Why is sexual reproduction such a common and successful adaptation for many different groups of organisms?

Part 2:

Although there are many freshwater and marine algal groups, Consider the difference in coloration of the red alga, brown alga, and green alga while you answer the following questions:

1.) Why do you think each group has different colors?

2.) What evolutionary advantages or disadvantages do you think these differences may provide?

Part 3:

Consider the adaptations necessary for plants in the water to land transition.

1.) What do you think would be some of the major problems that plants would need to contend with in various terrestrial (as opposed to aquatic) environments? Consider, for example, factors such as reproduction, structural support, water and nutrient transport systems, water conservation, and gas exchange. Please discuss (you can also make a table if you think that is easier) how each of the major groups of plants (seedless non-vascular, seedless vascular, and seed vascular plants) deals with these issues.

Part 4:

1. Examine the diagram of the moss life cycle. The sporophyte generation is smaller, and is nutritionally dependent on the gametophyte. Gametophytes come in two sexes: one producing small, motile male gametes in a structure called an antheridium; the other producing larger, nonmotile female gametes in a structure called an archegonium (Figure 5.5).

1.) Why is the location of zygote formation an adaptation to living on land?

2.) How do the male and female gametes come in contact with each other?

2. Although mosses lack vascular tissue, some have specialized elongated cells that help transport water and fluids. Mosses also lack the hard material found embedded in the cell walls of most terrestrial plants.

1.) How does the moss sporophyte get water and energy?

2.) Why are mosses so small?

3.) How do mosses carry out gas exchange?

Part 5:

1. Examine the diagram of the fern life cycle. The sporophyte is by far the larger and more complex generation (see Figure 5.6). In ferns reproductive organs occur in clusters on the undersides of the leaves. The gametophyte is free-living, producing both male and female gametes. Within a gametophyte the male and female gametes mature at different times, which decreases the chance of self-fertilization. The sperm are flagellated and require water for locomotion.

1.) How do the male and female gametes come in contact with each other?

2.) What is required for this to happen?

2. Watch this video

1.) What is the function of the waxy cuticle?

2.) Why are the spores produced on the underside of the fronds?

3.) How does offspring dispersal occur?

4.) How do you think the vascular system has allowed ferns to grow larger than mosses?

Part 6:

Examine the photo of stomata above

1.) Why are stomata present in ferns but not in algae?

2.) What enters and leaves through the stomata?

3.) What conditions would result in stomata closing?

EXERCISE 6

1.) Can you explain why the female cones look different from the male cones?

2.) Why might some conifers have tough cones that are dependent on the heat of a fire to open up and disperse their seeds?

3.) Why do you think gymnosperms might be considered more successful than ferns in various terrestrial habitats? Is that necessarily true?

ANGIOSPERMS

1.) Why do you think carnivorous plants are found in nutrient poor soils?

Part 7:

Think about pollination for a few moments

1.) List one advantage and one disadvantage of having a generalist (something that pollinates many different flowers) versus a specialist (something that only pollinates one type of flower) pollinator for a plant.

2.) How do plants typically “reward” their pollinators? How does the plant benefit, and how does the pollinator benefit from this association?

Part 8: