Plant evolution and adaptations

What is the significance of evolution in systematics?

Evolution provides a firm scientific rationale for systematics.

What is a monophyletic group?

A group formed from the most recent common ancestor and all its descendants.

What is most systematic work informed by?

Morphology.

What is the cladistic view of plant evolution?

All plants are just green algae, and the origins of new groups are linked to key evolutionary innovations.

What does genomic data suggest about plant groups?

All major groups of plants are truly monophyletic.

How were bryophytes previously classified?

As a grade, gradually gaining more advanced plant traits.

What are the two main stages of a plant's life cycle?

Sporophyte and gametophyte.

What is a sporophyte?

A multicellular diploid organism that produces haploid spores.

What is a gametophyte?

A multicellular haploid organism that produces haploid gametes.

How do diploid sporophytes form?

By the fusion of two gametes.

What makes bryophytes unique among land plants?

They lack vascular tissues and have no lignin in their cell walls.

Where are bryophytes typically found?

In moist habitats.

What adaptation helps bryophytes limit dehydration?

A waxy cuticle.

How do bryophytes grow for additional support?

They grow in clumps.

What is the dominant stage in bryophytes?

The gametophyte stage.

Why do male bryophyte gametes require water?

To reach the female gametes.

What happens to the sporophyte in bryophytes?

It remains attached to the gametophyte.

What structures do fern gametophytes produce?

Both antheridia and archegonia on a single gametophyte.

How do ferns transport male gametes?

Through water.

What happens to the fern sporophyte after it develops roots?

It can soon live independently of the short-lived gametophyte.

What key adaptation do ferns have?

Vascular tissues and megaphylls.

What are lycophytes commonly known as?

Club mosses.

How many species of lycophytes exist today?

About 1,200 species.

What key adaptation do lycophytes have?

Vascular tissues and more complex leaf structures.

How do lycophytes compare to bryophytes in terms of life cycle?

They have a similar life cycle.

What was a major historical impact of lycophytes?

They were among the first plants to evolve tree-like sizes, forming forests in the Middle Devonian.

What advantages did seed plants pioneer?

A seed-based reproductive alternative and secondary growth of vascular tissues.

What advantage did secondary growth provide?

Stronger support and woody stems, allowing them to outcompete other forest-building trees.

What types of plants formed early forests?

Lycopsids and ferns.

How many species of gymnosperms exist?

About 1,000 species across four subclasses.

When did gymnosperms first emerge?

In the early Carboniferous period.

What does "heterosporous" mean?

Producing two sizes of spores: megaspores (female) and microspores (male).

How do gymnosperms transport microgametophytes?

Through pollen, which does not require water.

What replaced conifers as the main tree species?

Angiosperms (flowering plants).

What is a key reproductive feature of angiosperms?

The formation of nutritive endosperm tissue.

What happens when angiosperm pollen reaches the egg?

One sperm fertilizes the egg, and the other merges with binucleate central cells to form the endosperm.

What plays a key role in the high diversity of angiosperms?

Co-evolution.

What are the three types of xerophytes?

Drought escaping, drought evading, and drought tolerating.

What is the main characteristic of drought-escaping plants?

They only grow when water is available.

What is the main characteristic of drought-evading plants?

They enter dormancy during droughts.

What is the main characteristic of drought-tolerating plants?

They have extensive root systems to sustain growth during droughts.

What are key adaptations of cacti?

Slow growth to maintain activity after moisture drops, fine root systems to collect water effectively, enlarged succulent stems for water storage, leaves reduced to thorns for light reflection.

What is Crassulacean Acid Metabolism (CAM)?

A process where stomata open at night to collect CO₂, which is stored as malate and converted back during the day to avoid water loss.

What are hydrophytes?

Plants adapted to survive in highly humid environments.

Give an example of hydrophytes.

Fern trees in cloud forests.

How do hydrophytes regulate stomata?

They have high stomatal densities with inactive guard cells since they do not need to close.

What are aquatic plants called to distinguish them from algae?

Macrophytes.