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Bio exams > Exam 2 seeds > Flashcards

Exam 2 seeds Flashcards

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Biology 101 flashcards
1
Q

Intro to seed plants

A

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
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2
Q

Traits of seed plants

A
  • 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
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3
Q

Reduced gametophytes

A

Gametophytes of seed plants are typically microscopic

  • Remain within the sporangia of parental sporophyte
  • Depend on sporophyte for nutrition
  • Protection from UV and drying
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4
Q

Heterospory

A

Most (not all) seedless plants are homosporous

  • Seed plants are heterosporous

– Megasporangium -> megaspore -> ♀ gametophyte

– Microsporangium -> microspores -> ♂ gametophytes

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5
Q

Gametophytic relations

A

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
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6
Q

Ovules

A
  • 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

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7
Q

Pollen and Production of Sperm

A

Microspores develop into pollen grains, which contain male gametophytes

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8
Q

Pollination

A

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

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9
Q

seeds

A

A seed develops from the whole ovule

  • A seed is a sporophyte embryo, along with its food supply, packaged in a protective coat
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10
Q

Seed plants:
Gymnosperms and angiosperms

A

Gymnosperms means “naked seeds”

  • The seeds are exposed on sporophylls that form cones (strobili)
  • Angiosperm seeds are found in fruits, which are mature ovaries
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11
Q

Gymnosperm origin & evolution

A

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
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12
Q

Diversity of gymnosperms

A
  • 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)
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13
Q

Phylum Cycadophyta

A

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
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14
Q

Phylum Ginkgophyta

A

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
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15
Q

Phylum Gnetophyta

A
  • This phylum comprises three
    genera: Gnetum, Ephedra and
    Welwitschia
  • Species vary in appearance, and some are tropical whereas others live in deserts
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16
Q

Genus Welwitschia

A

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

17
Q

Genus Gnetum

A

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

18
Q

Genus Ephedra

A

40 species
-Arid regions
-Global
-Ephidrine

19
Q

Phylum Coniferophyta

A

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

  • Most conifers are evergreens and can carry out photosynthesis year round
20
Q

Three key features of the gymnosperm life cycle:

A

-Dominance of the sporophyte generation

– Development of seeds from fertilized ovules

– The transfer of sperm to ovules by pollen

21
Q

Pine life cycle 30.5

A

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
22
Q

Phylum Anthophyta

A

All angiosperms are in this phylum

  • Antho = flower, phyta = plant
  • Angio = container, sperm = seed
23
Q

Flowers fig 30.8

A

An angiosperm structure specialized for sexual
reproduction

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

24
Q

Complete and incomplete flowers

A

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

25
Q

Angiosperm-pollinator
coevolution

A
  • 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
26
Q

Fruits

A

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
27
Q

The Angiosperm Life Cycle 38.4

A
  • 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
28
Q

Archaefructus sinensis

A

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

29
Q

Angiosperm phylogeny

A

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

Bio exams (7 decks)

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