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Biology > Plant Diversity II > Flashcards

Plant Diversity II Flashcards

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1
Q

How long ago was the evolution of seeded plants?

A
  • About 360 MYA
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2
Q

What were some of the main evolutionary innovations of seed plants?

A
  • Further gametophytes miniaturization
  • Produce 2 kinds of spores (“heterospory”)
  • Specialised structures to protect the gametophyte
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3
Q

What are the two kinds of heterospory?

A
  • Seed plants produce 2 kinds of spores (“heterospory”):
    » Megaspore: gives rise to female gametophyte
    » Microspore: gives rise to male gametophyte
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4
Q

What are the specialised structures in seed plants used to protect the gametophyte?

A

» Megaspore encased in protective and food layers (called “ovule”)
• Megaspore gives rise to female gametophyte, which stays sheltered in the ovule
• Once fertilized, it becomes the “seed”
» Microspore encased within pollen wall, which contains sporopollenin → resistant to drying (called “pollen grain”)
• Microspore gives rise to male gametophyte, sheltered within pollen grain

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5
Q

Which is dominant in non vascular plants, Gametophyte or sporophyte?

A
  • Gametophyte is dominant

- Sporophyte is reduced and so the plant is dependant on gametophyte for nutrition

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6
Q

Which is dominant in seedless vascular plants, Gametophyte or sporophyte?

A
  • Sporophyte is dominant

- Gametophyte is reduced and so the plant is independent (Photosynthetic and free-living)

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7
Q

Which is dominant in seeded vascular plants, Gametophyte or sporophyte?

A
  • Sporophyte is dominant

- Gametophyte is reduced (usually microscopic) and so plant is dependant on surrounding sporophyte tissue for nutrition.

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8
Q

How are the egg and sperm produced in seeded plants?

A
  • Diploid sporophyte produce haploid spore by meiosis:
    » Megaspore → egg (within the ovule)
    » Microspore → sperm (within pollen grain, generally without flagella)
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9
Q

How does reproduction of seeded plants work?

A
  • Only pollen grain leaves parent plant
    » Pollen grain reaches and enters pollen tube of ovule (“pollination”)
    » Pollen nucleus reaches egg and fuses (“fertilisation”) → seed
    » New sporophyte grows out of the seed
  • No independent gametophyte organism
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10
Q

Explain the anatomy of an unfertilized ovule.

A
  • A megasporangium is surrounded by a protective layer of tissue called an integument.
  • This megasporangium surrounds the spore containing the egg.
  • The micropyle is the only opening through the integument and allows entry of a pollen grain.
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11
Q

What is the process of fertilising the egg of a seed?

A
  • A megaspore develops into a female gametophyte, which produces an egg.
  • The pollen grain, which had entered through the micorpyle, contains male gametophyte.
  • The male gametophyte develops a pollen tube that discharges sperm, thereby fertilising the egg and creating a Gymnosperm seed.
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12
Q

What is a Gymnosperm seed?

A
  • Fertilisation initiates the transformation of the ovule into a seed, which consists of a sporophte embryo, a food supply and a protective seed coat derived from the integument.
  • The megasporangium dries out and collapses.
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13
Q

Draw the diagram of the formation of a gymnosperm seed

A

book

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14
Q

What distiguishes seeded plants?

A
  • Internal fertilisation and protection of the embryonic sporophyte (seed) distinguishes these plants → adaptation to dry spells
    » Later innovation, make it appealing for animals → increases dispersal, and discarded in favourable location
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15
Q

What are the benefits of a pollen grain?

A
  • Pollen grain resistant to drying and can travel by wind or hitchhike on animal → removes the dependence on water for sperm transport → allows plants to colonise dry environments
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16
Q

What are the two clades of seed plants?

A
  • Gymnosperms
    » “gymno” (bare, naked) and “sperm” (seed) → “naked seed”
    » Seeds exposed
  • Angiosperms
    » “angeion” (vessel, container) and “sperm” (seed) → “contained seed”
    » Seeds contained in fruit
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17
Q

What are the differences between Gymnosperms and Angiosperms?

A
  • Wood structure
  • Different pollen
  • Gymnosperms lack flowers
  • Gymnosperms dominant flora in Mesozoic (245–65 mya), angiosperms have dominated the Cenozoic, particularly since late Eocene (40 mya)
  • Gymnosperms have 4 phyla, angiosperms only 1
  • Angiosperms account for over 99.5% of all “higher plants” (seed plants) species
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18
Q

What are the three key features of the Gymnosperm life cycle?

A
  • Miniaturisation of gametophyte, dominance of the sporophyte generation
  • Development of resistant, dispersible seeds from fertilised ovules
  • The transfer of sperm to ovules by airborne pollen grains
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19
Q

If Pine is a gymnosperm what does it use to reproduce?

A
  • Pine trees are heterosporous: produce male spores (microspores) and female spores (megaspores) by meiosis
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20
Q

how does the reproduction of a pine work?

A
  • Pollen reaches ovule → pollen germinates forming pollen tube that digests its way to megaspore; meanwhile megaspore produces haploid gametophyte; pollen nucleus reaches egg → fertilisation → seed → seedling → mature sporophyte → releases spores
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21
Q

What is the history of Gymnosperms?

A
  • Early gymnosperms lived in moist Carboniferous alongside seedless plants (which require moisture for reproduction)
  • As climate dried in the Permian (299-252 mya), gymnosperms thrived, and dominated terrestrial ecosystems until the end of the Mesozoic era (66 mya)
22
Q

How many Phyla of Gymnosperms are there?

A
  • 4 extant gymnosperm phyla
23
Q

Provide a summary on Conifers

A
  • Gymnosperms = Phylum Coniferophyta
  • Largest phylum (600 species)
  • Cone-bearing
  • Perennial (long-living) woody plants
  • Most are trees, but a few are shrubs
  • Highly adaptable (arid lands, high latitudes)
  • Conifers
    » Seen as more primitive compared to flowering plants, but …
    » Grow in all parts of the world (4 families in Australia and NZ)
    » Dominate in forests in the wettest, coldest and highest parts of the world
    » Total area of coniferous forest exceeds that of flowering plants
24
Q

What are four examples of Australian Conifers?

A
  • Bunya pine (Araucaria Bidwillii)
  • Wollemi pine (Wollemia nobilis)
  • Tasmania Cedar (Athrotaxis Cupressoides)
  • Pine tree (pinus radiata)
25
Q

Give a brief summary on Cycads

A
  • Gymnosperm =Phylum Cycadophyta
  • 300 species
  • Palm-like plants
    » True palms are angiosperms
  • Single upright, usually unbranched trunk
  • Long feathery (“pinnate”) leaves
  • Large seeds (up to 15kg)
  • Separate male and female individuals (“dioecious”)
  • Most endangered of all plant group
    » 75% of species threatened by habitat destruction
26
Q

Give a summary of Phylum Gnetophyta

A
  • Gymnosperm = Phylum Gnetophyta
  • Poorly known and understood group
  • 75 species, 3 genera: Gnetum, Ephedra and Welwitschia
  • Group united by very similar floral morphology, and considered the link between gymnosperms and angiosperms
27
Q

Give a summary of Phylum Ginkgophyta

A
  • Gymnosperm = Phylum Ginkgophyta
  • Single living species Ginkgo biloba
  • Remnant of once flourishing Cretaceous flora
  • Only wild population located in western China
  • Tolerates pollution, commonly planted in cities
  • Dioecious (individual trees have either male or female organs)
    » Female produces edible seeds, but rotting seed has pungent smell (!)
    » Usually only pollen producing males planted
28
Q

Give a summary of Anigosperms

A
  • Most diverse and widespread of all plants
    » Approximately 250,000 known species, covering 11,000 genera; 275 families and 49 orders
    » Dominate nearly all terrestrial ecosystems
  • Highest productive capacity
  • Recognised by two key adaptations and unique reproductive structures: flowers and fruits
29
Q

What is a flower?

A
  • Unique structure for sexual reproduction
  • Specialised shoot with up to 4 types of modified leaves:
    » Sepal
    » Petal
    » Stamen
    » Carpel
30
Q

How is pollen transferred from one plant to another?

A
  • In many species, insects and other animals transfer pollen from one flower to sex organ of another
    » Overcomes randomness of wind dependent pollination of gymnosperms
    » Some angiosperms still wind pollinated
31
Q

What are the four types of modified leaves in a flower?

A

» Sepal: green, enclose the flower before it opens
» Petal: brightly colored to attract pollinators if not wind-pollinated
» Stamen: produce microspores → pollen grain with male gametophyte (stored in anther)
» Carpel: “container” where megaspores produced → female gametophyte
• Stigma, style (canal) and ovary (contains one or more ovules)

32
Q

draw the diagram of a flower

A

book

33
Q

Where are flowers derived from

A
  • All living flowers ultimately derive from a single ancestor that lived about 140 million years ago, a study suggests.
34
Q

What is the difference between the seed and the fruit?

A

After fertilisation:
» Ovule → seed
» Ovary → fruit

35
Q

What are the different textures of fruit?

A

Fruit can be:
» Fleshy (eg, peach, tomato, apple)
» Dry (eg, cereal grain of corn, rice, wheat; nuts)

36
Q

What does the fruit do?

A

Fruit protects seeds and helps in their dispersal

37
Q

What is the first stage of the Angiosperm Life cycle?

A
  • Flower = sporophyte composed of male and female structures
  • Male gametophytes contained in pollen grains produced by the sporangia of anthers
  • Female gametophyte = embryo sac, develops in ovule in ovary at base of stigma
38
Q

What is the main purpose of a flower?

A
  • Most flowers - mechanisms to ensure cross-pollination between flowers on different plants
39
Q

What happens in the second stage of the Angiosperm life cycle?

A
  • Pollen grain land on stigma, germinates and pollen tube grows down to the ovary
  • Pollen tube discharges two sperm cells into the female gametophyte within an ovule (double fertilisation)
40
Q

What is the third stage of the Angiosperm life cycle?

A
  • One sperm fertilises egg, while other combines with two nuclei in the central cell of female gametophyte and initiates development of food- storing endosperm
41
Q

What happens in the fourth stage of Angiosperm life cycle?

A
  • Triploid endosperm nourishes developing embryo
  • Within a seed, the embryo consists of a root and two seed leaves called cotyledons
  • The ovary develops into a fruit to help seed dispersal
42
Q

What are the main two groups of angiosperms?

A
  • One phylum, but >250,000 species of living angiosperms

- Two particularly large groups: monocots and eudicots

43
Q

Provide a summary of Monocots.

A
  • a group of Angiosperms
  • “mono” = one “cotyl” = cup or socket
  • About a third of angiosperm species (70,000)
  • Lilies, grasses and palms
  • Predominantly small plants, lacking true wood or secondary thickening of stems/branches
  • Large diversity
    » From 35 m palms to 0.1 mm floating weed (Wolffia)
44
Q

What are some examples of Monocots?

A

» Wheat, corn, grasses, orchids, sedges, papyrus, lilies, pineapples, palm trees and irises
- Wolffia globosa – smallest flowering plant (0.1 mm)

45
Q

Give a summary of Eudicots

A
  • “eu” = true, “di” = two, “cotyl” = cup or socket
  • Two thirds of angiosperm species (180,000)
  • The “typical” trees and shrubs, plus many herbs and legumes
  • Large diversity also, from Eucalyptus regnans (>90m) to smallest herb
46
Q

What are some examples of Eudicots?

A

» Banksias, eucalypts, acacia, figs, roses, daises, peas, apples, pears, cabbage, mangoes, grasses

47
Q

What is the Australian diversity of Eudicots?

A
  • ANZ flora comprise a few species-rich families
    » High degree of endemism (80-84% of species occur only in ANZ)
    » 75% of Australia is dominated by eucalyptus and acacia
48
Q

What are the four main reasons why Angiosperms are successful?

A
  1. Traits that made them resistant to drought and cold
  2. Very efficient vascular system
  3. Efficient reproduction (flower and fruit)
  4. Huge amount of diversity in chemistry
49
Q

What is the first reason why Angiosperms are successful?

A
  1. Traits that made them resistant to drought and cold
    » Tough leaves that can be lost when it gets cold (“deciduous”), reduced in size, efficient internal systems, tough seed coat
50
Q

What is the 2nd reason why Angiosperms are successful?

A
  1. Very efficient vascular system
    » Efficient conduction of sugars throughout the plant in phloem
    » Efficient transport of water in xylem (tracheids + special water conducting cells called “vessel elements”)
51
Q

What is the 3rd reason why Angiosperms are successful?

A
  1. Efficient reproduction (flower and fruit)
    » Precise method of pollination and seed dispersal, which allows them to exist as widely scattered individuals in many habitats
52
Q

What is the 4th reason why Angiosperms are successful?

A
  1. Huge amount of diversity in chemistry

» Increased defense mechanisms (against herbivores for example)

Biology (27 decks)

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