Exam 2 seeds

Question 1

Intro to seed plants

Answer 1

A seed consists of an embryo and nutrients surrounded by a protective coat

• Seed plants originated about 360 MYA
• Seeds enabled their bearers to become dominant producers in most terrestrial ecosystems
• Domestication of seed plants had begun by 8,000 years ago and allowed for permanent settlements

Question 2

Traits of seed plants

Answer 2

• Seeds and pollen key adaptations to life on
  land
• In addition to seeds, the following are common to all
  seed plants
  – Reduced gametophytes
  – Heterospory
  – Ovules
  – Pollen

Question 3

Reduced gametophytes

Answer 3

Gametophytes of seed plants are typically microscopic

• Remain within the sporangia of parental sporophyte
• Depend on sporophyte for nutrition
• Protection from UV and drying

Question 4

Heterospory

Answer 4

Most (not all) seedless plants are homosporous

• Seed plants are heterosporous

– Megasporangium -> megaspore -> ♀ gametophyte

– Microsporangium -> microspores -> ♂ gametophytes

Question 5

Gametophytic relations

Answer 5

Female gametophyte develops within an ovule

• Male gametophyte develops within a pollen grain
• Fertilization of ovule with pollen grain leads to the development of a seed

Question 6

Ovules

Answer 6

• An ovule consists of a megasporangium, megaspore, and one or more protective
  integuments
• Gymnosperm megaspores have one integument
• Angiosperm megaspores usually have two integuments

fig

Question 7

Pollen and Production of Sperm

Answer 7

Microspores develop into pollen grains, which contain male gametophytes

Question 8

Pollination

Answer 8

is transfer of pollen to part of a seed plant containing ovules

Question 9

seeds

Answer 9

A seed develops from the whole ovule

• A seed is a sporophyte embryo, along with its food supply, packaged in a protective coat

Question 10

Seed plants:
Gymnosperms and angiosperms

Answer 10

Gymnosperms means “naked seeds”

• The seeds are exposed on sporophylls that form cones (strobili)
• Angiosperm seeds are found in fruits, which are mature ovaries

Question 11

Gymnosperm origin & evolution

Answer 11

Progymnosperms acquire some adaptations that characterize seed plants (but not others)

Angiosperms began to replace gymnosperm

• Angiosperms now dominate more terrestrial ecosystems
• Today, cone-bearing gymnosperms called conifers dominate in the northern latitudes

Question 12

Diversity of gymnosperms

Answer 12

• Four extant phyla
  – Cycadophyta (cycads)– Ginkgophyta (one living species: Ginkgo biloba)– Gnetophyta (three genera: Gnetum, Ephedra, Welwitschia)– Coniferophyta (conifers, such as pine, fir, and redwood)

Question 13

Phylum Cycadophyta

Answer 13

Large cones and palmlike leaves

• Thrived during the Mesozoic, but relatively few species exist today

Unlike most seed plants, cycads have flagellated sperm

• Individuals have large cones and palmlike leaves

Question 14

Phylum Ginkgophyta

Answer 14

Consists of a single living species, Ginkgo biloba

• Like cycads, has flagellated sperm
• It has a high tolerance to air pollution and is a popular ornamental tree

Question 15

Phylum Gnetophyta

Answer 15

• This phylum comprises three
  genera: Gnetum, Ephedra and
  Welwitschia
• Species vary in appearance, and some are tropical whereas others live in deserts

Question 16

Genus Welwitschia

Answer 16

Only one species
-Desert plant
-SW Africa
-Leaves among the largest of all plants
-dioecious

Question 17

Genus Gnetum

Answer 17

~35 species
-Tropics
-Trees, shrubs, vines
-Look similar to
flowering plants
–seeds resemble fruits

Question 18

Genus Ephedra

Answer 18

40 species
-Arid regions
-Global
-Ephidrine

Question 19

Phylum Coniferophyta

Answer 19

By far the largest of the gymnosperm phyla
– ~3/4 of gymnosperm spp.

• Most conifers are evergreens and can carry out photosynthesis year round

Question 20

Three key features of the gymnosperm life cycle:

Answer 20

-Dominance of the sporophyte generation

– Development of seeds from fertilized ovules

– The transfer of sperm to ovules by pollen

Question 21

Pine life cycle 30.5

Answer 21

The pine tree is the sporophyte and produces sporangia in male and female cones

• Small cones produce microspores called pollen
  grains, each of which contains a male gametophyte
• The familiar larger cones contain ovules, which produce megaspores that develop into female gametophytes
• It takes well over two years from cone production to mature seed

Question 22

Phylum Anthophyta

Answer 22

All angiosperms are in this phylum

• Antho = flower, phyta = plant
• Angio = container, sperm = seed

Question 23

Flowers fig 30.8

Answer 23

An angiosperm structure specialized for sexual
reproduction

Flower = specialized shoot with up to 4 types of modified leaves

Question 24

Complete and incomplete flowers

Answer 24

Complete flowers have
– Stamens
– Carpel
– Petals
– Sepals

perfect, or bi flowers have male and female parts (stamens and carpel

Incomplete flowers are missing one or more of the four
-grasses dont have petals

Question 25

Angiosperm-pollinator coevolution

Answer 25

* Coevolution is the evolution of interacting species in response to changes in each other * Many flowering plants have coevolved with specific pollinators * For example, Darwin correctly predicted a moth with a 28 cm long tongue based on the morphology of a particular flower

Question 26

Fruits

Answer 26

Typically consists of a mature ovary but can also include other flower parts * Protect seeds and aid in dispersal * Mature fruits can be either fleshy or dry – Wall of ovary (pericarp) becomes soft = fleshy – Doesn’t = dry * Beans * Nuts * Grains

Question 27

The Angiosperm Life Cycle 38.4

Answer 27

* Sporophyte flowers are composed of both male and female structures * Male gametophytes are contained within pollen grains produced by the microsporangia of anthers * Female gametophyte, or embryo sac, develops within an ovule contained within an ovary at the base of a stigma * Most flowers have mechanisms to ensure crosspollination between flowers from different plants of the same species

Question 28

Archaefructus sinensis

Answer 28

Chinese fossils of 125-million-year-old angiosperms share some traits with living angiosperms but lack others * May belong to the earliest-diverging group of angiosperms E.g., Archaefructus sinensis has anthers and seeds within closed carpels but lacks petals and sepals

Question 29

Angiosperm phylogeny

Answer 29

The ancestors of angiosperms and gymnosperms diverged about 305 million years ago