Chapter 30 Plant Diversity 2 Flashcards
What is a seed?
A seed consists of an embryo and nutrients surrounded by a protective coat.
Where do gametophytes develop?
develop within the walls of spores and are retained within tissues of the parent sporophyte
List five characteristics common to all seed plants
- Seeds
- Reduced gametophytes
- heterospory
- ovules
- pollen
What is a gametophyte?
the multicellular haploid stage
What is a sporophyte?
the multicellular diploid stage
Describe the gametophyte and sporophyte of mosses and other non-vascular plants.
Gametophyte- dominant
Sporophyte- reduced, dependent on gametophyte for nutrition
Describe the gametophyte and sporophyte of ferns and other seedless vascular plants.
Gametophyte- reduced independent
Sporophyte- dominant
Describe the gametophyte and sporophyte of seed plants.
Gametophyte- reduced, depended on sporophyte tissue for nutrition
Sporophyte- dominant
What is heterospory?
plants that produce two kinds of spores: megaspores and microspores
Seed plants are _____
heterosporous
What are megasporangia and microsporangia?
- Megasporangia produce megaspores that give rise to female gametophytes.
- Microsporangia produce microspores that give rise to male gametophytes.
What are the parts of an ovule?
megasporangium, megspore, and one or more integuments
What does a fertilized ovule become?
a seed
What occurs inside each ovule?
inside each ovule a female gametophyte develops from a megaspore and produces one or more eggs
What does a microspore develop into?
a microspore develops into a pollen grain that consists of a male gametophyte enclosed within the pollen wall
How many integuments do gymnosperms and angiosperms have?
Gymnosperm megaspores have one integument.
Angiosperm megaspores usually have two integuments.
Describe the structure of an unfertilized ovule.
- Megaspore (n)
- Spore wall
- Megasporangium (2n)
- Integument
What is pollination?
Pollination is the transfer of pollen from the male to the female part containing the ovules.
What are advantages of pollen over free swimming sperm?
- Pollen eliminates the need for a film of water and can be dispersed great distances by air or animals.
- If a pollen grain germinates, it gives rise to a pollen tube that discharges two sperm into the female gametophyte within the ovule.
What are evolutionary advantages of seeds over spores?
They may remain dormant for days to years, until conditions are favorable for germination.
They may be transported long distances by wind or animals.
What are the three parts of a gymnosperm seed?
- seed coat derived from integument
- food supply (female gametophyte tissue) (n)
- embryo (2n)(new sporophyte)
What defines a gymnosperm?
The gymnosperms have “naked” seeds not enclosed by ovaries and exposed on modified leaves - cones
What are the 4 phyla of gymnosperms?
- Cycadophyta (cycads)
- Gingkophyta (one living species: Ginkgo biloba)
- Gnetophyta (three genera: Gnetum, Ephedra, Welwitschia)
- Coniferophyta (conifers, such as pine, fir, and redwood).
What are the two clades of see plants?
Seed plants can be divided into two clades: gymnosperms and angiosperms
What are cone bearing gymnosperms called?
conifers
What are three key feature of the gymnosperm life cycle?
- Dominance of the sporophyte generation.
- The transfer of sperm to ovules by pollen.
- Development of seeds from fertilized ovules.
What are angiosperms?
Angiosperms are seed plants with reproductive structures called flowers and fruits.
What is a flower?
flower is an angiosperm structure specialized for sexual reproduction
What are the four modified leaves of the flower?
- Sepals - enclose the flower
- Petals - brightly colored and attract pollinators
- Stamens - produce pollen on their terminal anthers
- Carpels - consist of an ovary containing ovules at the base and a style holding up a stigma, where pollen is received.
What are the two parts of the stamen?
Anther- terminal sac where pollen is produced
Filament-stalk that supports the anther
What are the three parts of the carpel?
Stigma, style, ovary
What does a fruit consist of?
A fruit typically consists of a mature ovary but can also include other flower parts.
What is the function of fruits?
Fruits protect seeds and aid in seed dispersal.
Fruits may either be ____ or ____.
Fleshy or dry
Give three examples of fruit adaptations for seed dispersal.
wings, seeds within berries, barbs
Where are male gametophytes found in angiosperms?
Male gametophytes are contained within pollen grains produced by the microsporangia of anthers.
Where are female gametophytes found within angiosperms?
The female gametophyte = embryo sac, develops within an ovule contained within an ovary at the base of a stigma.
What occurs when pollen lands on a stigma?
A pollen grain that has landed on a stigma germinates and the pollen tube of the male gametophyte grows down to the ovary.
How does pollen enter the ovary?
Sperm enter the ovule through a pore opening called the micropyle.
When does double fertilization occur?
Double fertilization occurs when the pollen tube discharges two sperm into the female gametophyte within an ovule.
What two events occur during double fertilization?
- One sperm fertilizes the egg forming a zygote.
- The other sperm combines with two nuclei (producing a triploid cell) and initiates development of food-storing endosperm.
What is the function of the endosperm?
endosperm nourishes the developing embryo
What makes up the embryo of a seed?
Within a seed, the embryo consists of a root and two seed leaves called cotyledons
What diverged 305 million years ago?
the ancestors of angiosperms and gymnosperms
What plants may angiosperms be closely related to?
Bennettitales- extinct seed plants with flowerlike structures
What two plants descended from two of the most ancient angiosperm lineages?
amborella and water lilies
What are the two largest groups of angiosperms?
Monocots and eudicots
Monocots (1/4)- one cotyledon
Eudicots (2/3)- two cotyledons
Describe monocot features.
- one cotyledon
- veins parallel
- vascular tissue scattered
- root system fibrous (no main root)
- pollen grain with one opening
- floral organs in multiples of 3
Describe eudicot features
- two cotyledons
- veins netlike
- vascular tissue arrange in a ring
- root system taproot
- pollen grain with three openings
- floral organs usually in multiples of 4 or 5
What are the two types of pollination?
self pollination and cross pollination
What is the evolutionary advantage of cross pollination?
enhances genetic variability
What is cross pollination?
when angiosperms transfer pollen from an anther on one plant to a stigma on another
Which clade has more species?
Clades with bilaterally symmetrical flowers have more species than those with radially symmetrical flowers
Describe four ways humans rely on plants.
- Most of our food comes from angiosperms. Six crops (wheat, rice, maize, potatoes, cassava, and sweet potatoes) yield 80% of the calories consumed by humans.
- Modern crops are products of relatively recent genetic change resulting from artificial selection.
- Many seed plants provide wood.
- Secondary compounds of seed plants are used in medicines.
List 5 ancestors in descending order.
Charophyte green algae, mosses, ferns, gymnosperms, angiosperms
