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Life of Earth 2 > Angiosperm reproduction and floral diversification > Flashcards

Angiosperm reproduction and floral diversification Flashcards

1
Q

What are flowers?

A

Reproductive shoots of angiosperm sporophytes

Composed of 4 whorls of modified leaves = floral organs

Determinate shoots

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2
Q

What are the 4 floral organs?

A

Sepals
Petals
Stamens
Carpels

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3
Q

The evolution of what is a defining feature of angiosperms?

A

Evolution of the closed carpel

enclosed ovule

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4
Q

What are the 3 variations of ovary positioning?

A 
Hypogynous
- above point where sepals + petals join 
= superior ovary 
Perigynous
- half-superior/half-inferior
Epigynous 
- inferior ovary
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5
Q

What are the 2 types of floral symmetry?

A

Actinomorphic
= radially symmetrical
Zygomorphic
= bilaterally symmetrical

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6
Q

How do zygomorphic flowers coevolve with their pollinators?

A

Specialise a petal to provide a landing pad to a specific pollinator

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7
Q

What is the calyx?

What is the corolla?

A

All the sepals

All the petals

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8
Q

What are the 5 types of flowers?

A 
>Complete = has all 4 floral organs
>Incomplete = lacks 1 or more floral organs
>Perfect = hermaphrodite 
>Imperfect = has either male or female reprod. structures (monoecious + dioecious)

> Inflorescences = clusters of flowers

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9
Q

What does the alternation of generations mean?

A

Plants have multicellular diploid + haploid phases

Gametophyte produces gametes

Sporophyte produces diploid spores

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10
Q

What is the trend in gametophyte size in evolution?

A

Reduction in size from moss > ferns > seed plants

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11
Q

What are the key features of the angiosperm life cycle?

A

Sporophyte = dominant

Gametophytes = reduced + depend of sporophyte for nutrients

Characterised by 3 Fs:
flowers
double fertilisation
fruits

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12
Q

What does double fertilisation produce?

A

Endosperm

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13
Q

Describe the development of the male gametophyte in pollen grain

A

Microsporangium contains microsporocytes

-> 4 microspores via meiosis
(joined in a tetrad)

-> male gametophyte via mitosis
(= 3 sperm cells + 1 vegetative cell)

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14
Q

Describe the development of the female gametophyte

A

Megaspore undergoes meiosis

-> 3 die + 1 megaspore survives

-> female gametophyte via mitosis
(7 cells + 8 nuclei)

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15
Q

What are the 3 pollination syndromes?

A

Entomophily = insect

Anemophily = wind

Ornithophily = bird

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16
Q

What are the features of entomophily?

A

> bright petals
strong sweet smell
nectar-producing glands
nectar guides - lead insects to nectar

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17
Q

What are the features of anemophily?

A

> large stigmas outside flower
little-no smell
large non-sticky pollen
no showy petals

18
Q

What are the features of ornithophily?

A

> long tube-shaped flowers
normally bright red/yellow flowers
no smell
nectar

19
Q

How do pollen tubes grow towards the ovule in order to carry out double fertilisation?

A

Specific chemical messengers guide the pollen to allow efficient delivery of non-motile sperm to egg

20
Q

What happens after double fertilisation?

A

Polarised growth of the embryo within walls of the ovule become the seed

Each ovule develops into a seed

Ovary develops into a fruit

21
Q

What encloses the embryo + seed?

A

A hard, protective seed coat

22
Q

What is the benefit of seed dormancy?

A

Increases chances of seed germinating at the appropriate time
-> increases chance of survival

23
Q

What inhibits seed germination?

A

ABA

24
Q

What is the purpose of fruit?

A

Protects seeds

Aids seed dispersal by mitotic + abiotic vectors

25
Q

What does the diversity of form of fruit depend on?

A

Shape of ovary from which it’s formed

Extent to which ovary wall (pericarp) expands

26
Q

What are the 3 layers of pericarp?

A

Exocarp
Endocarp
Mesocarp

27
Q

What are the 2 main categories of fruit?

A

Dry - fruit dries at maturity

Fleshy - ovary becomes thick, soft + sweet at maturity

28
Q

How can fruits be classified by their type of development?

A

Simple - single or several fused carpels from 1 flower

Aggregate - single flower w/ multiple separate carpels

Multiple - inflorescence

Accessory fruit - contains other floral parts in addition to ovaries

29
Q

What are the 4 fruit dispersal mechanisms?

A

Hydrochory = water

Anemochory = wind

Zoochory = animals

Autochory = by itself e.g. exploding

30
Q

When is asexual reproduction beneficial?

Why is this?

A

In a stable environment

Clones are vulnerable to local extinction if environment changes or disease

31
Q

What does sexual reproduction enable?

A

Generate genetic variation that makes evolutionary adaptation possible

32
Q

What are the 3 mechanisms of asexual reproduction?

A

Fragmentation
Root suckering
Apomixis (agamospermy)

33
Q

What is fragmentation?

A

Separation of a parent plant into parts that develop into whole plants

34
Q

what is root suckering?

A

Developing adventitious shoots from the root system

-> gives rise to separate plants

35
Q

What is apomixis?

A

Asxual production of seeds from a diploid cell

no fusion of sperm + egg

36
Q

Why does the hermaphrodite flower create an issue?

A

Potential for inbreeding depression

37
Q

What are the 3 developmental mechanisms for preventing self-fertilisation?

A

Dioecy = separate sexes in separate plants

Monoecy = separate sexes in separate flowers on same plant

Dichogamy = sequential hermaphroditism
= stamens + carpels mature at diff times

38
Q

What is the molecular genetic mechanism for preventing self-fertilisation?

A

Self-incompatibility

= plant recognises + rejects own pollen

39
Q

Why are angiosperms so diverse?

A

> evolution of closed carpel + hermaphrodite flower
-> allowed for diversification in mating systems

> coevolution w/ pollinators + dispersers

> control of mating partner

40
Q

Why are angiosperms so successful?

A

> evolution of carpel = protection of ovules + developing embryo

> double fertilisation
-> production of endosperm = food reserve for embryo

> hermaphrodite flower

> adaptations that facilitate genetic diversity via outbreeding

41
Q

Describe the taxonomy of angiosperms

A

Floral characteristics take priority over vegetative characteristics when allocating to genera or families

Life of Earth 2 (20 decks)

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