Gymnosperms and Angiosperms

What are seeds and pollen key adaptations for?

They protect from drought and UV radiation; allow reproduction without water.

What key reproductive adaptations do angiosperms have?

Flowers and fruits.

Why does human welfare depend on plants?

Plants provide food, fuel, medicine, oxygen, and ecosystem services.

What is a seed?

An embryo with stored nutrients enclosed by a protective coat.

How can seeds disperse?

By wind, water, or animals, often over long distances.

What is a reduced gametophyte?

A microscopic gametophyte dependent on sporophyte, developing within spores inside sporangia. (Dependent embryo)

What is heterospory?

Production of megaspores (female) and microspores (male); rule among seed plants.

What is an ovule?

A structure with a megaspore inside a megasporangium surrounded by protective tissue; angiosperms have two integuments.

What is pollen?

The male gametophyte enclosed within a pollen wall. Outside is diploid, inside is haploid

What is pollination?

Transfer of pollen to the part of the plant containing ovules, often without water.

What is a pollen tube?

A tube grown by germinated pollen that delivers sperm into the female gametophyte.

What is the evolutionary advantage of seeds over spores?

Seeds are multicellular, provide nourishment (embryo), can remain dormant, and disperse farther than spores.

How does an ovule become a seed?

After fertilization, the ovule develops into a seed: an embryo with a food supply in a coat.

What defines gymnosperms?

Seed plants with “naked seeds” not enclosed in fruit, often in cones.

What are conifers?

Cone-bearing gymnosperms; most are evergreens with needlelike leaves.

Briefly describe the gymnosperm life cycle.

Sporophyte makes cones → pollen cones produce microspores → pollen grains form male gametophytes → ovulate cones produce megaspores → fertilization → seed → germination into new sporophyte.

How long can gymnosperm seed development take?

Nearly 3 years from pollination to mature seed.

List key steps in gymnosperm reproduction.

Male cones → microspores → pollen → female cones → megaspores → female gametophyte → fertilization → zygote → embryo in seed.

Name four gymnosperm phyla.

Cycads, Ginkgo, Gnetophytes, and Conifers.

What are cycads?

Gymnosperms with large cones and palm-like leaves.

What is unique about Ginkgo biloba?

Only living Ginkgo species; male trees common due to rancid smell of fleshy seeds.

What are gnetophytes?

A group with three genera (Gnetum, Ephedra, Welwitschia); diverse habitats.

What is Ephedra used for?

Source of ephedrine, a nasal decongestant.

What are conifers notable for?

They are the largest gymnosperm phylum, mostly evergreen, with woody or sometimes fleshy cones.Needle-like leaves

What is a deciduous conifer example?

Bald cypress.

What are angiosperms?

Seed plants with flowers and fruits; the most diverse plant group.

What are flowers?

Reproductive structures specialized for pollination and fertilization.

What are sepals?

Usually green, enclose and protect the flower bud.

What are petals?

Brightly colored structures that attract pollinators.

What are stamens?

Male floral organs (microsporophylls) with a filament and anther.

What are carpels?

Female floral organs (megasporophylls) with ovary, style, and stigma. (Stigma→Style→Ovary)

What is a fruit?

A matured ovary wall containing seeds, aiding protection and dispersal.

What are fleshy fruits?

Fruits like grapes that are soft and edible.

What are dry fruits?

Fruits like nuts that are hard and dry at maturity.

How do fruits and seeds disperse?

By wind (dandelions), water (coconuts), or animals (clinging burrs, ingestion).

Briefly describe the angiosperm life cycle.

Anther produces microspores → pollen grains → stigma → pollen tube → double fertilization → zygote (2n) and endosperm (3n) → seed → sporophyte embryo.

What is double fertilization?

One sperm fertilizes egg (central)→ zygote (2n); the other fuses with two nuclei (polar)→ endosperm (3n) as food supply.

What is endosperm?

A triploid (3n) tissue that nourishes the developing embryo.

What are cotyledons?

Seed leaves; monocots have one, dicots have two.

What are basal angiosperms?

Earliest-diverging lineages with small flowers, such as water lilies.

What are magnoliids?

Spirally arranged floral organs; more closely related to monocots than basal angiosperms.

What are monocots?

Angiosperms with one cotyledon; include orchids, grasses, and palms. Parallel veins

What are eudicots?

True dicots with two cotyledons; most angiosperms, including legumes and roses. Branched veins

When did angiosperms diverge from gymnosperms?

About 305 million years ago.

What role did pollinators play in angiosperm evolution?

Co-evolution with animals increased speciation and diversity.

What products do seed plants provide humans?

Food crops, livestock feed, beverages (tea, coffee, chocolate), spices, paper, fuel, medicines.