Angiosperm reproduction and floral diversification

Question 1

What are flowers?

Answer 1

Reproductive shoots of angiosperm sporophytes

Composed of 4 whorls of modified leaves = floral organs

Determinate shoots

Question 2

What are the 4 floral organs?

Answer 2

Sepals
Petals
Stamens
Carpels

Question 3

The evolution of what is a defining feature of angiosperms?

Answer 3

Evolution of the closed carpel

enclosed ovule

Question 4

What are the 3 variations of ovary positioning?

Answer 4

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

Question 5

What are the 2 types of floral symmetry?

Answer 5

Actinomorphic
= radially symmetrical
Zygomorphic
= bilaterally symmetrical

Question 6

How do zygomorphic flowers coevolve with their pollinators?

Answer 6

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

Question 7

What is the calyx?

What is the corolla?

Answer 7

All the sepals

All the petals

Question 8

What are the 5 types of flowers?

Answer 8

>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

Question 9

What does the alternation of generations mean?

Answer 9

Plants have multicellular diploid + haploid phases

Gametophyte produces gametes

Sporophyte produces diploid spores

Question 10

What is the trend in gametophyte size in evolution?

Answer 10

Reduction in size from moss > ferns > seed plants

Question 11

What are the key features of the angiosperm life cycle?

Answer 11

Sporophyte = dominant

Gametophytes = reduced + depend of sporophyte for nutrients

Characterised by 3 Fs:
flowers
double fertilisation
fruits

Question 12

What does double fertilisation produce?

Answer 12

Endosperm

Question 13

Describe the development of the male gametophyte in pollen grain

Answer 13

Microsporangium contains microsporocytes

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

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

Question 14

Describe the development of the female gametophyte

Answer 14

Megaspore undergoes meiosis

-> 3 die + 1 megaspore survives

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

Question 15

What are the 3 pollination syndromes?

Answer 15

Entomophily = insect

Anemophily = wind

Ornithophily = bird

Question 16

What are the features of entomophily?

Answer 16

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

Question 17

What are the features of anemophily?

Answer 17

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

Question 18

What are the features of ornithophily?

Answer 18

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

Question 19

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

Answer 19

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

Question 20

What happens after double fertilisation?

Answer 20

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

Each ovule develops into a seed

Ovary develops into a fruit

Question 21

What encloses the embryo + seed?

Answer 21

A hard, protective seed coat

Question 22

What is the benefit of seed dormancy?

Answer 22

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

Question 23

What inhibits seed germination?

Answer 23

ABA

Question 24

What is the purpose of fruit?

Answer 24

Protects seeds

Aids seed dispersal by mitotic + abiotic vectors

Question 25

What does the diversity of form of fruit depend on?

Answer 25

Shape of ovary from which it's formed | Extent to which ovary wall (pericarp) expands

Question 26

What are the 3 layers of pericarp?

Answer 26

Exocarp Endocarp Mesocarp

Question 27

What are the 2 main categories of fruit?

Answer 27

Dry - fruit dries at maturity Fleshy - ovary becomes thick, soft + sweet at maturity

Question 28

How can fruits be classified by their type of development?

Answer 28

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

Question 29

What are the 4 fruit dispersal mechanisms?

Answer 29

Hydrochory = water Anemochory = wind Zoochory = animals Autochory = by itself e.g. exploding

Question 30

When is asexual reproduction beneficial? Why is this?

Answer 30

In a stable environment Clones are vulnerable to local extinction if environment changes or disease

Question 31

What does sexual reproduction enable?

Answer 31

Generate genetic variation that makes evolutionary adaptation possible

Question 32

What are the 3 mechanisms of asexual reproduction?

Answer 32

Fragmentation Root suckering Apomixis (agamospermy)

Question 33

What is fragmentation?

Answer 33

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

Question 34

what is root suckering?

Answer 34

Developing adventitious shoots from the root system | -> gives rise to separate plants

Question 35

What is apomixis?

Answer 35

Asxual production of seeds from a diploid cell | no fusion of sperm + egg

Question 36

Why does the hermaphrodite flower create an issue?

Answer 36

Potential for inbreeding depression

Question 37

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

Answer 37

Dioecy = separate sexes in separate plants Monoecy = separate sexes in separate flowers on same plant Dichogamy = sequential hermaphroditism = stamens + carpels mature at diff times

Question 38

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

Answer 38

Self-incompatibility | = plant recognises + rejects own pollen

Question 39

Why are angiosperms so diverse?

Answer 39

> evolution of closed carpel + hermaphrodite flower -> allowed for diversification in mating systems > coevolution w/ pollinators + dispersers > control of mating partner

Question 40

Why are angiosperms so successful?

Answer 40

> 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

Question 41

Describe the taxonomy of angiosperms

Answer 41

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