Lecture 24 Flashcards
What are angiosperms? and when did they first evolve?
• c. 250,000 species (note, only 600 species of conifers) Why? • Dominate most terrestrial ecosystems • Basis of world agriculture • Origin in Early Cretaceous (130 million years ago); dominant by 65 million years ago) reproduce by flowers -much more diverse than conifers -dominate almost everywhere but not in arborial trees -enormous diversity of sizes and morphology… –there are more types of eucalypt flowers than conifers
What are the flowers for?
-to attract pollinators
Why are angiosperms so incredibly successful?
1) Vegetative or morphological features 2) Reproductive features
What are the vegetative or morphological features of angiosperms that make them so successful?
-• Vessels in xylem: large, thin-walled, with open ends - continuous piping system. Fiber cells for strength. • Sieve cells (no nuclei) controlled by companion cells (with nuclei) in phloem -tracheids found in some primitive flowering plants (provide structure and support as well) -but still the piping system doesn’t explain why are they so much more succesful than conifers
How many species of flowering plants are there?
250 000 species of flowering plants
Do angiosperms have sporophyte or gametophyte dominance?
-complete sporophyte dominance
How is reproduction achieved in angiosperms?
• Double fertilization: 1) one gives rise to the embryo, 2) other gives rise to the endosperm (food reserves, but only if fertilized!) • Pollination diverse mechanisms (e.g., wind, insects); many are specific.
Describe the reproductive system of angiosperms.
• Stamens (male) • Carpels (female)
consists of ovary, ovules, style and stigma
• Pollen lands on stigma surface; pollen tube grows to the ovule
• Angiosperms - seed in a vessel (refers to the carpel).
angiosperm= means seed in a vessel
self incompatibility= can’t have sex withe themselves= leads to greater variability, females develop at different types, stigma recognises cell from non cells so as to not self fertilise
Describe the ovule in gymnosperms and angiosperms:
Describe the process by which the sperm gets to the egg:
Describe the first and second fertilization:
Why is the reproduction of angiosperms advantageous?
advantages of angiosperm= double fertilisation, quicker seed set, self incompatibility
-fruit=
seed is set in months not years= as in conifers where it take 2 years for seed to emerge
fruit like a fertliser for the seed= when shit of birds
=good for dispersal
three layers in grapes and peach, seed, flesh and skin
-in apples=layers derived from flower and supporting leaves
Describe the life cycle of an angiosperm:
What do ovules and carpels develop into?
Ovules develop into seeds Carpel wall develops into fruit
What are fruits for?
- dispersals of seeds
- grizzly bears= eat berries= dispersal
=co evolutionary thing bears and berries
- in Australia= ants are important dispersers, the seeds have sticky bit they eat but take them to their nest so= dispersal
- the sticky seeds= get on your clothes and fur
Why is wind pollination more limited?
wind pollination= need large population to fertilise
-conifers do it
What mechanisms do angiosperms use to pollinate?
• Diverse mechanisms (e.g., wind, water, insects, birds, mammals); many are specific, such as the orchids.
coconuts= water dispersal, last for months in water
wind pollination causes athma and alergies!
What are the pollination strategies of orchids?
-this one, flower looks like a female insect so the males try to have sex= get pollen all over and disperse it
- orchids are rare, almost all have specific pollinators= co evolution, can’t take them away!
- then the orchid which smells like meat= so bugs come
also an orchid=moves when the insect lands= moves it to the pollen (Stylidium)
- whack!
- takes 20 min to load
List 4 adaptive features that my have lead to the dominance of angiosperms over other land plants and state their advantages?
endosperm, pollination, self incompatibility…fruit
What is Flowering Plant Diversity?
- Taxonomy(e.g.,eudicotsv. monocots)
- Ecologically (aquatic, terrestrial, xerophytic)
- Morphologically (carnivory, parasitic)
- Biogeography (Australian flora, Gondwana)
What are the two basic flower types?
-count flower parts
if the same width on the bottom and top= monocots
What are the differences betweed monocots and dicots?
seeds are different when germinate
-dicots= cotyledons
-venation in leaves, dicots= network of veins
dicots= secondary growth in circles, monocotes= not as much, as vascular bundle is dispersed in the plant
List some examples of monocots and dicots:
monocots: orchids, palms, grasses
dicots: eucalyptus,acacia, peas, buttercups, daisies, banksia
What are some parasitic angiosperms?
- mistletoe (on eucalypts and conifers eg)
- rafflesia
Why are some angiosperms carnivorous?
-when not enough nutrition, supplement it by ingesting organisms
What are the characteristics of the modern Australian flora?
23-till present million yrs ago
angiosperms dominant
-most conifers decline except cypress family
- Northerly drift of Aust but climatic cooling.
- Aridification & decline of rainforests.
- Fire-adapted floras; low-nutrient adaptations
(The winners during drying of the continent: Family: Proteaceae (Banksias, grevilleas, hakeas etc) - adapted to low-nutrient soils)
