Gymnosperms: Concepts Review

Flashcards covering key concepts of gymnosperms, including features of vascular and seed plants, homospory vs. heterospory, gymnosperm characteristics, reproductive processes (gamete formation, pollination, fertilization), and definitions of related terms found in Chapter 26 of the required textbook.

What is an advantage of having vascular tissues in plants?

Vascular tissues allow for efficient transport of water and nutrients, enabling plants to grow taller, compete for light, and effectively colonize diverse habitats.

What is an advantage of having the sporophyte as the dominant generation in vascular plants?

The dominant sporophyte generation possesses true stems, leaves, and

roots and evolved sporophylls → Modified

leaves that bear spores

Why are vascular tissues considered a key innovation in plant evolution?

Vascular tissues are a key innovation because they enabled plants to grow tall,

What are two advantages of forming seeds in plant reproduction?

Seeds offer protection for the embryo, provide stored food for germination, facilitate dispersal over long distances, and allow for dormancy during unfavorable conditions.

Why are seeds considered a key innovation in plant evolution?

Seeds are a key innovation because they offer enhanced embryo protection, nutrient supply, dormancy, and efficient dispersal, allowing plants to successfully colonize new and drier environments.

Differentiate between homospory and heterospory, and identify which is characteristic of seed plants.

Homospory is the production of one type of spore that develops into a bisexual gametophyte. Heterospory is the production of two types of spores (microspores and megaspores) that develop into separate male and female gametophytes, which is characteristic of seed plants (gymnosperms and angiosperms).

What are the main phyla of gymnosperms?

The main phyla of gymnosperms are Cycadophyta, Ginkgophyta, Coniferophyta, and Gnetophyta.

What are the basic characteristics of gymnosperms?

Gymnosperms are seed-bearing plants with 'naked' seeds (not enclosed within a fruit), typically have cones, exhibit heterospory, and possess a dominant sporophyte generation.

What types of sporophylls are found in gymnosperms?

Gymnosperms have microsporophylls, which bear microsporangia, and megasporophylls, which bear megasporangia.

Describe the general steps involved in the formation of a male gamete (sperm) from a microsporophyll in gymnosperms.

From a microsporophyll, microsporangia produce microsporocytes, which undergo meiosis to form microspores. Each microspore develops into a pollen grain (the male gametophyte), which contains cells that will eventually produce sperm.

Describe the general steps involved in the formation of a female gamete (egg) from a megasporophyll in gymnosperms.

From a megasporophyll, an ovule contains a megasporangium with a megasporocyte. The megasporocyte undergoes meiosis to produce usually one surviving megaspore, which develops into the female gametophyte (containing the archegonium with the egg cell).

In gymnosperms, what is the male gametophyte and what is the female gametophyte?

The male gametophyte is the pollen grain, and the female gametophyte is the structure developed from the megaspore within the ovule, which contains the archegonium with the egg cell.

Why is the evolution of the pollen grain considered a key innovation in plant evolution?

The pollen grain is a key innovation because it eliminated the need for water for sperm transport, enabling seed plants to colonize drier terrestrial environments more effectively.

What is pollination in gymnosperms?

Pollination in gymnosperms is the transfer of pollen grains from the male cone (microsporangia) to the female cone (containing ovules).

How does fertilization occur in gymnosperms, and where does the embryo form?

Fertilization occurs when sperm from the pollen grain fertilizes the egg within the archegonium of the female gametophyte, which is inside the ovule. The resulting zygote develops into an embryo within the ovule, ultimately forming a seed.

Define 'micropyle'.

The micropyle is a small opening in the integuments of an ovule through which pollen often enters.

Define 'integuments'.

Integuments are the protective outer layers covering the ovule, which develop into the seed coat after fertilization.

Define 'ovule'.

The ovule is the structure in seed plants that contains the megasporangium and female gametophyte, and ultimately develops into a seed after fertilization.

Define 'megasporangium'.

A megasporangium is a sporangium that produces megaspores.

Define 'microsporangium'.

A microsporangium is a sporangium that produces microspores.

Define 'microsporocyte' (or microspore mother cell).

A microsporocyte is a diploid cell within the microsporangium that undergoes meiosis to produce haploid microspores.

Define 'megasporocyte' (or megaspore mother cell).

A megasporocyte is a diploid cell within the megasporangium that undergoes meiosis to produce haploid megaspores.

Define 'microspore'.

A microspore is a haploid spore that develops into a male gametophyte, which is the pollen grain.

Define 'megaspore'.

A megaspore is a haploid spore that develops into a female gametophyte within the ovule.

Define 'archegonia'.

Archegonia are the female reproductive organs in gymnosperms, located within the female gametophyte, each containing an egg cell.

Briefly describe the major stages in the life cycle of a gymnosperm.

The sporophyte (mature tree) produces male and female cones. Male cones produce pollen grains (male gametophytes). Female cones contain ovules, where megaspores develop into female gametophytes with eggs. Pollination occurs, followed by fertilization to form a zygote, which matures into an embryo within a seed. The seed then germinates into a new sporophyte.