Plant Diversity II Flashcards
1
Q
How long ago was the evolution of seeded plants?
A
- About 360 MYA
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
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
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
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
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)
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.
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)
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
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.
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.
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.
13
Q
Draw the diagram of the formation of a gymnosperm seed
A
book
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
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
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
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
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
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
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
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
Give a brief summary on Cycads
- 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
Give a summary of Phylum Gnetophyta
- 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
Give a summary of Phylum Ginkgophyta
- 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
Give a summary of Anigosperms
- 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
What is a flower?
- Unique structure for sexual reproduction
- Specialised shoot with up to 4 types of modified leaves:
» Sepal
» Petal
» Stamen
» Carpel
30
How is pollen transferred from one plant to another?
- 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
What are the four types of modified leaves in a flower?
» 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
draw the diagram of a flower
book
33
Where are flowers derived from
- All living flowers ultimately derive from a single ancestor that lived about 140 million years ago, a study suggests.
34
What is the difference between the seed and the fruit?
After fertilisation:
» Ovule → seed
» Ovary → fruit
35
What are the different textures of fruit?
Fruit can be:
» Fleshy (eg, peach, tomato, apple)
» Dry (eg, cereal grain of corn, rice, wheat; nuts)
36
What does the fruit do?
Fruit protects seeds and helps in their dispersal
37
What is the first stage of the Angiosperm Life cycle?
- 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
What is the main purpose of a flower?
- Most flowers - mechanisms to ensure cross-pollination between flowers on different plants
39
What happens in the second stage of the Angiosperm life cycle?
- 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
What is the third stage of the Angiosperm life cycle?
- 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
What happens in the fourth stage of Angiosperm life cycle?
- 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
What are the main two groups of angiosperms?
- One phylum, but >250,000 species of living angiosperms
| - Two particularly large groups: monocots and eudicots
43
Provide a summary of Monocots.
- 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
What are some examples of Monocots?
» Wheat, corn, grasses, orchids, sedges, papyrus, lilies, pineapples, palm trees and irises
- Wolffia globosa – smallest flowering plant (0.1 mm)
45
Give a summary of Eudicots
- “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
What are some examples of Eudicots?
» Banksias, eucalypts, acacia, figs, roses, daises, peas, apples, pears, cabbage, mangoes, grasses
47
What is the Australian diversity of Eudicots?
- 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
What are the four main reasons why Angiosperms are successful?
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
What is the first reason why Angiosperms are successful?
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
What is the 2nd reason why Angiosperms are successful?
2. 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
What is the 3rd reason why Angiosperms are successful?
3. 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
What is the 4th reason why Angiosperms are successful?
4. Huge amount of diversity in chemistry
| » Increased defense mechanisms (against herbivores for example)
