Biology 200: Chapter 22 Gymnosperms

Flashcards covering the characteristics, anatomy, reproduction, and human relevance of various gymnosperm phyla including Pinophyta, Ginkgophyta, Cycadophyta, and Gnetophyta.

According to the transcript, when did the oldest known seeds appear?

Late Devonian, more than $350$ million years ago

What were the first seed plants, which were fernlike in appearance?

Pteridosperms (seed ferns)

What does the term "gymnosperm" refer to?

The exposed nature of the seeds

Where are gymnosperm seeds produced in contrast to flowering plants?

On the surface of sporophylls or similar structures instead of enclosed within a fruit

How are seed-bearing and pollen-bearing sporophylls often arranged in gymnosperms?

In cones

What structure contains the nucellus in the female gametophyte?

An ovule

What does the integument of the ovule become after fertilization?

The seed coat

How does the growth of a gymnosperm female gametophyte differ from that of ferns?

It does not grow independently, but develops within sporophyte structures

How many living phyla are there in the gymnosperms?

$4$ living phyla

Which phylum is characterized by distinct strobili and needlelike leaves arranged in clusters?

Phylum Pinophyta

Approximately how many species are in the Phylum Pinophyta?

About $600$ species

Which phylum has notched, broad, fan-shaped leaves with evenly forked veins?

Phylum Ginkgophyta

Which phylum is described as a cross between a tree fern and a palm?

Phylum Cycadophyta

What unique xylem components are found in the Phylum Gnetophyta?

Vessels and tracheids

What is the largest genus of conifers?

Pines ($\text{Pinus}$)

Which trees are considered the world's oldest known living organisms?

Bristlecone pines

What is a cluster of needlelike pine leaves called?

A fascicle

What are fascicles in terms of shoot structure and growth?

They are short shoots with restricted growth

Where is the hypodermis located in a pine leaf?

Below the epidermis

How many layers of thick-walled cells typically comprise the hypodermis in pines?

One to two ($1-2$) layers

What description is given to pine stomata to indicate adaptation for harsh conditions?

Recessed or sunken

What are the functions of pine resin?

It is antiseptic and aromatic, preventing development of fungi and deterring insects

What type of fungi are associated with the roots of most conifers?

Mycorrhizal fungi

Why is conifer wood considered "softwood"?

Thick-walled cells are absent

What wood components are present in "hardwood" (dicot) trees but absent in conifers?

Thick-walled vessels and fibers

What do pollen cones (male strobili) consist of?

Papery or membranous scales

Where are the microsporangia located on the scales of a pollen cone?

In pairs toward the bases of scales

Of how many cells and air sacs does a pine pollen grain consist?

$4$ cells and a pair of air sacs

What is the purpose of air sacs on pollen grains?

To add buoyancy in wind

Where are the megasporangia located in seed cones?

Within ovules, at the bases of seed cone scales

What is the physical description of the scales of seed cones?

Woody scales with inconspicuous bracts between

What are the three components of a pine ovule?

A megasporangium containing a nucellus and a single megasporocyte

What is the pore in the integument of an ovule called?

The micropyle

What is produced when a megasporocyte undergoes meiosis?

Four ($4$) megaspores

How many megaspores survive to develop into the female gametophyte?

One ($1$) megaspore (three degenerate)

Where does the female gametophyte develop archegonia?

At the micropyle end

How long do pine seed cones take to mature?

$2$ years

During the first year, what do pollen grains catch on after oozing from the micropyle?

Sticky pollen drops

What constitutes a mature male gametophyte in pines?

A germinated pollen grain with a pollen tube and two ($2$) sperm

What is notable about the motility of pine sperm?

Sperm have no flagella

Is an antheridium formed during pine reproduction?

No

During the second year of development, where does the pollen tube arrive?

At the archegonium

What happens to the two sperm when they enter the archegonium?

One sperm unites with the egg to form a zygote, and the other sperm degenerates

What nourishes the pine embryo?

The female gametophyte

Which conifers produce ovules singly at the tips of shoots?

Yew ($\text{Taxus}$) and California nutmeg ($\text{Torreya}$)

What is the fleshy, cuplike structure surrounding the ovule in Yews?

An aril

What are the seed characteristics of the Southern hemisphere conifer Podocarpus?

Fleshy-coated seeds with a large appendage at the base

What is specific about the appearance of juniper seed cones?

They are fleshy

What is the only living species in the phylum Ginkgophyta?

$$\text{Ginkgo biloba}$$

How do the veins in Ginkgo leaves branch?

Dichotomously

What does the term "dioecious" mean in the context of Ginkgo and Cycads?

Male and female structures are on separate trees

Which phylum contains slow-growing plants with tall unbranched trunks and pinnately divided leaves?

Phylum Cycadophyta

What characterizes the genus Gnetum?

Vine-like plants with broad leaves found in the tropics

What are the features of the species Welwitschia?

Short stem, long taproot, and only two ($2$) straplike leaves that become tattered

What pharmaceutical use is mentioned for the drug taxol derived from yew trees?

Treatment for ovarian cancer