BIO 193 Exam I Terms and Vocabulary

From __________ to bryophytes: how plants colonized the land

green algae

What are the advantageous of plants being on land? (5 things)

• abundant and high-quality sunlight

• earlier access to CO₂

• Reduced predation in early stages

• Rick nutrients in soil

• Potential for upright growth and branching

What are some challenges to being on land as a plant?

• dehydration (dry out)

• lack of structural support against gravity

• challenge to transport water and nutrients

• difficult to engage in gas exchange for photosynthesis

What are the closest living relatives of plants?

Charophytes

What are charophytes?

Charophytes are the only present-day algae that share certain distinctive traits with plants, suggesting that they are the closest living relatives of plants.

What are some similarities between charophytes and plants?

the cells of both plants and charophytes have distinctive circular rings of proteins embedded in the plasma membrane

What is the Casparian strip?

The Casparian strip is a band of suberin (waxy material) found in the cell walls of endodermal cells. It blocks the passive flow of water and solutes through the cell walls (apoplast), forcing them to cross cell membranes. This allows the plant to selectively control what enters the vascular system (xylem).

What were the major developments in the evolution of plants, from water (algae) to life on land?

reproductive structures, photosynthetic branches, structures that anchor the plant to the soil

Name the three types of terrestrial plants

Nonvascular plants, seedless vascular plants, seed plants

What is an example of a nonvascular plant?

mosses

What is an example of a seedless vascular plant?

ferns

What are some examples of seed plants?

cone-bearing plants and flowering plants

What is sporopollenin?

A layer of durable polymer in charophytes that prevents exposed zygotes from drying out. Allowed algae to survive periods when they were not submerged

What is the Alternation of Generations?

The life cycle of all plants which alternate between two generations of distinct multicellular organisms: sporophytes and gametophytes. Each generation gives rise to the other.

When are plants in the haploid stage?

After meiosis and before fertilization

When are plants in the diploid stage?

After fertilization and before meiosis

Does the alternation of generations occur in charophytes?

No

In order to engage in the alternation of generations, an organism’s life cycle must include both _______________ and __________________

multicellular haploid stage; multicellular diploid stage

What is a gametophyte?

Literally means “gamete-producing plant”

Multicelular haploid (n)

Relates to the alternation of generations

The multicellular haploid gametophyte is named for it production by ___________ of haploid gametes that fuse during fertilization, forming diploid zygotes

mitosis

What does a gametophyte produce?

haploid gametes

How does a gametophyte produce two haploid gametes?

through mitosis

Two gametes unite (fertilization) and form a…

diploid zygote

is a zygote a diploid or haploid?

diploid (2n)

Mitotic division of a zygote produces…

a multicellular diploid sporophyte

What is a sporophyte?

“spore-producing plant”

2n

diploid

What mechanism allowed a mature sporophyte to produce unicellular haploid spores?

meiosis

After meiosis, spores develop into…

multicellular haploid gametophytes

Starting with a multicellular haploid gametophyte, explain the alternation of generations

multicellular haploid (n) gametophyte → Through mitosis, the gametophyte produces haploid gametes → two gametes unite (fertilization) and form a diploid (2n) zygote → Through meiosis, the zygote develops into a multicellular diploid sporophyte → after meiosis, the spores develop into multicellular haploid gametophytes

What is a spore?

reproductive cell capable of developing into a new individual without fusion with another reproductive cell

While spores can develop a new individual on their own, a ________ must fuse in pairs

gamete

What type of life cycle do plants have that includes multicellular embryos?

Alternation of generations

Where does the multicellular plant embryo develop?

Within the tissues of the female parent (gametophyte)

What is the embryo formed from?

a zygote

What is the role of the female parent’s tissues in embryo development?

They protect the embryo and provide nutrients

What types of nutrients are provided to the developing embryo?

Sugars and amino acids

What specialized cells help transfer nutrients to the embryo?

Placental transfer cells

How do placental transfer cells enhance nutrient transfer?

By having elaborate ingrowths of the cell wall surface

What structures form the ingrowths in placental transfer cells?

The plasma membrane and cell wall

Why are plants called embryophytes?

Because they have multicellular, dependent embryos

What is an embryophyte?

A plant that has a multicellular, dependent embryo retained within the parent tissue

Why did plants develop new adaptations after diverging from algal relatives?

To survive and reproduce on dry land

What does alternation of generations involve?

Multicellular forms that give rise to each other in turn

What structures produce spores in plants?

sporangia

In which stage of the plant life cycle are sporangia found?

The sporophyte stage

What do sporangia produce?

Spores

What is sporopollenin?

A polymer that makes spore walls resistant to harsh environments

Why is sporopollenin important for plant spores?

It allows them to survive and disperse in dry air

What are apical meristems?

regions of cell division at the tips of roots and shoots

What is the function of apical meristems?

They allow plants to grow longer roots and shoots

How do apical meristems help plants survive?

By increasing exposure to environmental resources

What is the function of the epidermis in plants?

It protects the plant body

Where are apical meristems located in a plant shoot?

At the tip of the shoot

What do cells produced by apical meristems do?

They differentiate into specialized cell types

What is the outer layer formed from apical meristem cells?

the epidermis

Besides the epidermis, what else do apical meristem cells form?

Various types of internal tissues

What is the cuticle in plants?

A waxy covering on the epidermis

What is the main function of the cuticle?

to prevent water loss

Why do plants need protection from desiccation?

Because they are exposed to air and can dry out

Besides preventing water loss, what else does the cuticle do

protects against microbial attack

What are stomata?

Specialized pores in plant surfaces

What is the function of stomata?

Gas exchange (CO₂ in, O₂ out)

How do stomata help with photosynthesis?

They allow CO₂ to enter the plant

What happens to stomata in hot, dry conditions?

They close to reduce water loss

What is the main way water leaves a plant?

through the stomata

did the earliest plants have true roots and leaves?

no

How did early plants absorb nutrients without roots?

through symbiotic relationships with fungi

What are mycorrhizae?

Symbiotic associations between plant roots (or early plants) and fungi

How do mycorrhizal fungi help plants?

They transfer nutrients from the soil to the plant

Why were mycorrhizae important for early plants?

They helped plants colonize land without roots

What types of algae are most closely related to plants?

unicellular and small colonial algae

Why do scientists study microscopic fossils to find early plants?

Because the first plants were likely small

When did plant spores first appear in the fossil record?

About 470 million years ago

How are early plant spores different from algal or fungal spores?

Their chemical composition matches modern plant spores

What structural feature links ancient spores to modern plants?

Features found in spores of liverworts

What evidence links early spores to plant tissue?

Spores found embedded in cuticle material

What are extant plant lineages?

Plant groups that still have living members

What is vascular tissue in plants?

Tubes that transport water and nutrients

What are vascular plants?

Plants with an extensive system of vascular tissue

What are nonvascular plants?

Plants without an extensive transport system

What are bryophytes?

Informal term for nonvascular plants like mosses, liverworts, and hornworts

What are the three types of plants?

Nonvascular plants (bryophytes), seedless vascular plants, seed plants

What are the two types of seed plants?

gynosperms and angiosperms

Angiosperms are ________ plants

flowering

What is a key difference between a group and a clade?

A group shares features, but a clade shares common ancestry

Do all members of a feature-based group share the same ancestry?

No

What does sharing a more recent common ancestor imply about traits?

They are more likely to share similar traits

What is a seed?

An embryo with stored nutrients inside a protective coat

What are seed plants?

A clade of vascular plants that produce seeds

What distinguishes gymnosperms from angiosperms?

Whether seeds are enclosed or not

Which type of seed plant has enclosed seeds?

Angiosperms

What are gymnosperms?

Plants with “naked” seeds not enclosed in chambers

What is a common example of gymnosperms?

Conifers (trees with pinecones)

Where do angiosperm seeds develop?

Inside chambers formed from flowers

What do paleobotanists study?

Fossils of ancient plants

Why are plant fossils important?

They show intermediate steps in plant evolution

What are bryophytes?

Nonvascular plants

What are the three phyla of bryophytes?

Liverworts, mosses, and hornworts

What type of plants are bryophytes (woody or nonwoody)

Nonwoody (herbaceous)

What are liverworts named after?

Their shape