BISC 120 Midterm 3 | 18 Plant Diversity and Seed Plants

What distinguishes bryophytes in the course comparison?

Mosses, liverworts, and hornworts lack vascular tissue and true roots. Their gametophyte is dominant and their sporophyte remains attached.

Why do both moss and fern sperm need a film of water?

Their flagellated sperm swim to the egg. Fern vascular tissue helps with transport and growth.

A plant has true roots, a dominant sporophyte, spores, and swimming sperm. What group fits?

Seedless vascular plants. Ferns are a representative example.

What do xylem and phloem transport, and how did vascular tissue change plant growth?

Xylem carries water and minerals. Phloem carries sugars and other solutes. Efficient transport allows taller growth.

What advantages did true roots and leaves provide?

Roots improve acquisition and movement of water and minerals. Leaves increase light capture.

How do microphylls and megaphylls differ?

A microphyll has a single vein. A megaphyll has branched vascular tissue.

In a fern diagram, which part is the sporophyte, which is the gametophyte, and what is a sorus?

The leafy fern is the sporophyte. The small heart-shaped plant is the independent gametophyte. A sorus is a cluster of sporangia.

What does homospory mean in the fern example?

One type of spore grows into a bisexual gametophyte.

Compare which generation dominates and whether the gametophyte is free-living in moss, fern, and seed plants.

Moss gametophytes dominate. Fern sporophytes dominate but their gametophytes can live independently. Seed-plant gametophytes are reduced and protected.

Which groups came to dominate first, and which formed the first forests?

Bryophytes pioneered land vegetation. Seedless vascular plants formed the first forests. Seed plants diversified later.

What innovations do all seed plants share in the lecture?

Reduced gametophytes, heterospory, ovules, pollen, and seeds.

What do microspores and megaspores develop into?

Haploid microspores become male gametophytes. Haploid megaspores become female gametophytes.

What are microsporangia and megasporangia?

Diploid structures in which meiosis makes haploid microspores and megaspores, respectively.

What is pollen, and how is it related to sperm?

Pollen contains the haploid male gametophyte. That gametophyte produces sperm and its pollen tube delivers them.

What is in an ovule, and where does the egg form?

Protective integuments surround a megasporangium. The megaspore develops into a female gametophyte inside the ovule, and the gametophyte produces an egg.

Trace pollination to fertilization and explain how pollen reduces dependence on water.

Pollination delivers pollen. Pollen germinates, a pollen tube grows toward the ovule, and sperm are delivered to fertilize the egg without an external film of water.

What becomes the embryo, seed, and seed coat?

A fertilized egg becomes a diploid zygote and then an embryo. The ovule becomes the seed. The integument forms the seed coat.

Trace the main stages of the pine life cycle.

The diploid sporophyte makes pollen and ovulate cones. Meiosis makes microspores and megaspores, which form gametophytes. Pollination and fertilization lead to a seed that can germinate into a new sporophyte.

How does a seed compare with a spore?

A seed packages a diploid embryo, food, and a protective coat for dormancy and dispersal. A plant spore is a single haploid cell.

Which generation provides the food reserve in the gymnosperm seed pictured in lecture?

The haploid female gametophyte nourishes the diploid embryo.

What does naked seed mean for gymnosperms?

Their seeds are exposed instead of enclosed by a fruit. In conifers, the seeds are borne on cone scales.

What distinguishes angiosperms, and when did they become widespread relative to gymnosperms?

They are flowering seed plants with fruits. They diversified after the earlier period of gymnosperm dominance and are now the most diverse plants.

What are the four main flower organs and their functions?

Sepals enclose the bud, petals often attract pollinators, stamens produce pollen, and carpels enclose ovules.

What two parts make up a stamen?

The anther produces pollen. The filament supports the anther.

What are the three carpel regions and what do they do?

The stigma receives pollen, the style connects it to the ovary, and the ovary contains ovules.

Where is the receptacle in a flower diagram?

At the base of the flower, where the floral organs attach.

In a pea pod, which part came from the ovary and which from the ovules?

The mature ovary forms the fruit, the pod. The ovules become the seeds, the peas.

How can fruits aid dispersal?

They protect seeds and can disperse them by wind, water, attaching to animals, or being eaten.

What was Darwin's abominable mystery in the lecture?

The rapid diversification of flowering plants. The lecture connects their success with floral innovations and coevolution.