BIOL204 Midterm 2 Lecture 17-19

What are the two major living clades of seed plants?

Gymnosperms and angiosperms

What does Spermatophyta mean?

The seed plants

What are the synapomorphies of seed plants?

Seeds, highly reduced gametophytes, heterospory, pollen, and ovules

What is heterospory?

The production of two different types of spores: megaspores and microspores

What do microspores develop into?

Male gametophytes enclosed within pollen grains

What do megaspores develop into?

Female gametophytes

What is an ovule?

A megasporangium, megaspore, and one or more protective integuments

How many integuments do gymnosperm ovules usually have?

One integument

How many integuments do angiosperm ovules usually have?

Two integuments

What are sporophylls?

Modified leaves that bear sporangia

What are megasporophylls?

Sporophylls that bear megasporangia

What are microsporophylls?

Sporophylls that bear microsporangia

What does gymnosperm mean?

Naked seed

What does angiosperm mean?

Encased seed

When did gymnosperms first appear in the fossil record?

Approximately 305 million years ago

During which era did gymnosperms dominate terrestrial ecosystems?

The Mesozoic Era

Why were gymnosperms better suited to drier conditions than nonvascular plants?

They had thick cuticles and needle-shaped leaves with reduced surface area

What is the adaptive advantage of needle-shaped leaves?

They decrease surface area and reduce water loss

What are the four living gymnosperm clades?

Cycadophyta, Ginkgophyta, Gnetophyta, and Coniferophyta

What are the main characteristics of cycads?

Large cones, palm-like pinnately compound leaves, flagellated sperm, and mostly tropical distribution

What type of cones do cycads have?

Female cones are much larger than male cones

Are cycads monoecious or dioecious?

Dioecious

What does dioecious mean?

Male and female reproductive structures occur on separate plants

How many living species of cycads are there approximately?

About 350 species

What percentage of cycad species are threatened?

Approximately 75 percent

What are the characteristics of Ginkgo biloba?

It is the only living ginkgo species, has flagellated sperm, fan-shaped deciduous leaves, and is dioecious

Why is Ginkgo biloba commonly planted in cities?

It has a high tolerance for air pollution

How many living species are in Ginkgophyta?

One species: Ginkgo biloba

What are the three genera of Gnetophyta?

Gnetum, Ephedra, and Welwitschia

What is Ephedra known for producing?

Ephedrine, a decongestant

Where is Welwitschia mirabilis found?

Only in the Namib Desert of Namibia and Angola

How does Welwitschia obtain moisture?

From fog

What are the characteristics of conifers?

Worldwide distribution, woody growth, cones, and needle-like or scale-like leaves

Are conifers monoecious or dioecious?

Usually monoecious

What does monoecious mean?

A single plant has both male and female reproductive structures

Approximately how many conifer species exist?

About 600 species

What are examples of conifers?

Pines, spruces, hemlocks, firs, cypresses, redwoods, giant sequoias, and yews

What is the oldest known bristlecone pine age range?

Approximately 5,000–7,000 years

What compound is produced by the Himalayan yew?

Paclitaxel, also called Taxol

What are the synapomorphies of angiosperms?

Flowers, fruits, enclosed ovules and seeds, double fertilization, triploid endosperm, and specialized conductive cells

How many angiosperm species exist?

More than 290,000–300,000 described species

What percentage of plant species are angiosperms?

Approximately 90 percent

When did angiosperms first appear?

At least 140 million years ago

What is a flower?

A specialized shoot containing modified leaves called floral organs

What are the four types of floral organs?

Sepals, petals, stamens, and carpels

What is the function of sepals?

They enclose and protect the developing flower

What is the function of petals?

They are often brightly colored and attract pollinators

What is the function of stamens?

They produce pollen and are the male reproductive structures

What is the function of carpels?

They produce ovules and are the female reproductive structures

What is another name for the female reproductive structure of a flower?

The pistil

What are the two parts of a stamen?

A filament and anther

What is the function of the filament?

It supports the anther

What is the function of the anther?

It produces pollen

What are the three parts of a carpel?

Stigma, style, and ovary

What is the function of the stigma?

It receives pollen

What is the function of the style?

It connects the stigma to the ovary and provides a pathway for the pollen tube

What is the function of the ovary?

It contains the ovules

What is a perfect flower?

A flower containing both stamens and carpels

What is a complete flower?

A flower containing sepals, petals, stamens, and carpels

What is an incomplete flower?

A flower missing one or more floral organs

What is a staminate flower?

A flower containing stamens but no functional carpels

What is a carpellate flower?

A flower containing carpels but no functional stamens

How does fertilization in gymnosperms compare with angiosperms?

Gymnosperm fertilization occurs long after pollination, while angiosperm fertilization occurs soon after pollination

How long can gymnosperm seeds take to mature?

Approximately one to two years

Why can angiosperms produce seeds rapidly?

Fertilization occurs soon after pollination

Where are male gametophytes located in angiosperms?

Inside pollen grains produced by microsporangia in anthers

Where does the female gametophyte develop in angiosperms?

Inside an ovule contained within the ovary

What is an embryo sac?

The female gametophyte of an angiosperm

What is pollination?

The transfer of pollen from anther to stigma

What are the agents of pollination?

Wind, water, insects, birds, bats, and other animals

Why do wind-pollinated plants produce large amounts of pollen?

Most pollen does not reach a stigma, so large quantities increase the chance of pollination

What is a pollen tube?

A tube that grows from a germinated pollen grain toward the ovary

What is the micropyle?

A pore in the integuments through which the pollen tube enters the ovule

What is double fertilization?

One sperm fertilizes the egg and the other sperm combines with two polar nuclei

What is produced when sperm fertilizes the egg?

A diploid zygote

What is produced when sperm combines with two polar nuclei?

Triploid endosperm

What is the function of endosperm?

It provides stored nutrition for the developing embryo

What is the chromosome number of angiosperm endosperm?

Triploid, or 3n

Why is double fertilization advantageous?

Food storage develops only when an ovule has been fertilized, reducing wasted nutrients

What structures make up the embryo inside a seed?

A root and two seed leaves called cotyledons

What are cotyledons?

Seed leaves that are part of the plant embryo

What is selfing?

Self-fertilization within the same plant or flower

Why do many angiosperms prevent selfing?

To promote cross-fertilization and increase genetic variation

How can dioecious plants prevent self-fertilization?

Their staminate and carpellate flowers occur on separate plants

How can plants prevent selfing through timing?

Their stamens and carpels mature at different times

How can flower structure prevent selfing?

Stamens and carpels may be positioned so that pollen cannot reach the stigma of the same flower

What is self-incompatibility?

The ability of a plant to reject its own pollen

How does self-incompatibility work?

A matching S-gene triggers a signal pathway that blocks pollen tube growth

What is gametophytic self-incompatibility?

Self-incompatibility in which the S allele of the pollen gametophyte determines whether fertilization is blocked

What is sporophytic self-incompatibility?

Self-incompatibility in which gene products on the pollen wall interact incompatibly with substances from the stigma

What is a fruit?

A mature ovary

What are the functions of fruits?

They protect dormant seeds and aid in seed dispersal

What is a vegetable botanically?

An edible plant part that is not a fruit or seed

What is a simple fruit?

A fruit that develops from one carpel or several fused carpels of one flower

What is an example of a simple fruit?

A pea fruit

What is an aggregate fruit?

A fruit that develops from several separate carpels of one flower

What is an example of an aggregate fruit?

A raspberry

What is a multiple fruit?

A fruit that develops from a group of flowers, or inflorescence

What is an example of a multiple fruit?

A pineapple

What is an accessory fruit?

A fruit containing floral parts in addition to the ovary