Lecture 24

Question 1

What are angiosperms? and when did they first evolve?

Answer 1

• 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

Question 2

What are the flowers for?

Answer 2

-to attract pollinators

Question 3

Why are angiosperms so incredibly successful?

Answer 3

1) Vegetative or morphological features 2) Reproductive features

Question 4

What are the vegetative or morphological features of angiosperms that make them so successful?

Answer 4

-• 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

Question 5

How many species of flowering plants are there?

Answer 5

250 000 species of flowering plants

Question 6

Do angiosperms have sporophyte or gametophyte dominance?

Answer 6

-complete sporophyte dominance

Question 7

How is reproduction achieved in angiosperms?

Answer 7

• 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.

Question 8

Describe the reproductive system of angiosperms.

Answer 8

• 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

Question 9

Describe the ovule in gymnosperms and angiosperms:

Answer 9

Question 10

Describe the process by which the sperm gets to the egg:

Answer 10

Question 11

Describe the first and second fertilization:

Answer 11

Question 12

Why is the reproduction of angiosperms advantageous?

Answer 12

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

Question 13

Describe the life cycle of an angiosperm:

Answer 13

Question 14

What do ovules and carpels develop into?

Answer 14

Ovules develop into seeds Carpel wall develops into fruit

Question 15

What are fruits for?

Answer 15

• 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

Question 16

Why is wind pollination more limited?

Answer 16

wind pollination= need large population to fertilise

-conifers do it

Question 17

What mechanisms do angiosperms use to pollinate?

Answer 17

• 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!

Question 18

What are the pollination strategies of orchids?

Answer 18

-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

Question 19

List 4 adaptive features that my have lead to the dominance of angiosperms over other land plants and state their advantages?

Answer 19

endosperm, pollination, self incompatibility…fruit

Question 20

What is Flowering Plant Diversity?

Answer 20

• Taxonomy(e.g.,eudicotsv. monocots)
• Ecologically (aquatic, terrestrial, xerophytic)
• Morphologically (carnivory, parasitic)
• Biogeography (Australian flora, Gondwana)

Question 21

What are the two basic flower types?

Answer 21

-count flower parts

if the same width on the bottom and top= monocots

Question 22

What are the differences betweed monocots and dicots?

Answer 22

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

Question 23

List some examples of monocots and dicots:

Answer 23

monocots: orchids, palms, grasses
dicots: eucalyptus,acacia, peas, buttercups, daisies, banksia

Question 24

What are some parasitic angiosperms?

Answer 24

• mistletoe (on eucalypts and conifers eg)
• rafflesia

Question 25

Why are some angiosperms carnivorous?

Answer 25

-when not enough nutrition, supplement it by ingesting organisms

Question 26

What are the characteristics of the modern Australian flora?

Answer 26

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)