Exam 2 Angiosperms

1. Describe the ancestral and derived/distinguishing traits of angiosperms.

• Ancestral traits: Vascular tissue, leaves, seeds, pollen, and microscopic gametophytes.

• Derived traits: Flowers, fruits, and double fertilization.

2. Are angiosperms vascular plants? Seed plants? Flowering plants? Explain.

Yes. Angiosperms are vascular plants because they have xylem and phloem, seed plants because they produce seeds, and flowering plants because they reproduce using flowers. Their seeds develop inside fruits.

3. Describe the main parts of a flower and the function(s) of each.

• Petals: Attract pollinators.

• Sepals: Protect the developing flower bud.

• Stamen (male part):

  • Anther: Produces pollen.

  • Filament: Supports the anther.

• Carpel (female part):

  • Stigma: Sticky tip that receives pollen.

  • Style: Stalk through which the pollen tube grows.

  • Ovary: Contains ovules, which develop into seeds after fertilization.

4. Describe the adaptive benefit of flowers with an emphasis on how “showy” flowers facilitate a mutualistically beneficial relationship between animals and flowers, and touch on the fact that co-evolution is involved. Including:

a. How does a showy flower attract pollinator?

b. How does a show flower keep pollinators returning to flowers?

c. How does the anatomy of a flower promote pollination?

Flowers help angiosperms reproduce by attracting animals that carry pollen between flowers.

A-Through bright colors, appearance, scent, and sometimes a place to lay eggs.

B- It rewards pollinators with nectar, pollen, or food and protection for their larvae.

C-The shape and arrangement of flower parts help pollen contact the pollinator and reach the stigma. Some flowers are adapted to specific pollinators.

Coevolution: Flowers and their pollinators can evolve together, developing matching features that make pollination more effective and specific.

5. How are the structures of a flower related to leaves (developmentally and phylogenetically)

Flower parts evolved from modified leaves. Petals are associated with leaves folded over pollen-producing structures, while carpels are modified leaves folded around egg-producing structures.

6. How is the use of showy flowers to promote pollination “better” than wind pollinations found in gymnosperms?

Animal pollination is more targeted and specific because animals carry pollen between flowers. Wind pollination wastes large amounts of pollen, while animal pollination can transfer pollen more efficiently.

7. How is an abiotically pollinated flower structurally different from an animal pollinated flower and why?

• Wind-pollinated: Usually small and non-showy, with no need to attract or reward animals. They may release large amounts of pollen.

• Animal-pollinated: Often colorful or scented, with structures that attract pollinators and help transfer pollen.

8. What is a specialist pollinator? A generalist?

• Specialist: Pollinates a specific flower type or a very limited number of species.

• Generalist: Pollinates a variety of flower types.

9. Describe the structure, function, and adaptive value of fruit and various ways in which both fleshy fruit and dry fruit carry out their seed dispersal functions.

A fruit usually develops from the flower's ovary after fertilization. It protects seeds and helps disperse them.

• Fleshy fruits: Use color, scent, and sweet pulp to attract animals that carry or disperse seeds.

• Dry fruits: Disperse seeds through wind, water, ejection from the fruit, or by attaching to animals.

10. What benefits do angiosperm traits offer over the traits of gymnosperms?

• Flowers allow targeted pollination by animals.

• Fruits protect seeds and help disperse them.

• Double fertilization prevents wasting resources on food reserves for unfertilized ovules.

11. Describe the process and significance of double fertilization? What are its benefits and what kind of life history strategy did it allow to develop in angiosperms?

Double fertilization occurs when two sperm participate in fertilization:

1. One sperm fertilizes the egg, forming a diploid zygote (2n2n) that develops into the embryo.

2. The other sperm fertilizes the two polar nuclei, forming triploid endosperm (3n3n), which provides nutrition.

Benefits: Food reserves develop only when fertilization occurs, reducing wasted energy. Seed development can also happen quickly, sometimes within one growing season, supporting annual plants.

13. Describe angiosperm life cycle including the relative length, size, and dependence or independence of the sporophyte and gametophyte generations including:

a. What is the male gametophyte

b. How is the pollen made

c. What is the female gametophyte

d. How is the embryosac made"

The sporophyte is the dominant, large, visible plant. The gametophytes are microscopic, reduced, and dependent on the sporophyte.

A-Pollen, which contains a tube cell and a generative cell.

B-The anther contains pollen sacs (microsporangia), where microspores develop into pollen through mitosis.

C-The embryo sac, located inside the ovule.

D-The ovule contains a female sporangium that produces a megaspore. The megaspore develops into the embryo sac, which contains an egg, two polar nuclei, two synergids, and three antipodal cells.