Week 5

Question 1

why is the seed so important

Answer 1

Capacity of the genome, or germination, producing new seedlings and plants

Evolutionary fitness

The seed has changed to course of plant evolution

Question 2

What are the seed plants

Answer 2

gymnosperms and angiosperms

Question 2

What are the 4 trait advances that lead to the seed

Answer 2

Reduced gametophyte stage: more in the sporophyte stage

Heterospory: spores give rise to EITHER male or female

Pollen: the way male gametes are transported to meet the immobile female gametes that are within the sporophyte

Ovules: within the female gametophyte that produced eggs that eventually become fertilized

Question 2

Seed plant evolution has included three key reproductive adaptations

Answer 2

1. The increasing dominance of the sporophyte
   
   2. The advent of the seed as a resistant, dispersible stage in the life cycle
   3. The appearance of pollen as an airborne agent that brings gametes together

Question 2

Microsporangia vs Megasporangium

Answer 2

Micro: contained within the pollen, microsporocytes undergoes meiosis to form haploid microspores

Mega: contained within the ovules, megasporocyte undergoes meiosis to form megaspores

Question 3

Layers of the naked seed

Answer 3

Seed coat (2n)
Megagametophyte (n) - consists of food reserves
Embryo (2n)

Question 4

Sexual reproduction of conifers

Answer 4

Meiosis and fertilization occur within the sporophyte by the developing ovules and pollens

Both the microspore and the megaspores go through meiosis
- The pollen grain slowly makes its way through the megasporangium while the megaspores goes through meiosis
-The surviving megaspore develops into the female gametophyte - contains two or three archegonia which will each form an egg
-Fertilization occurs, one zygote will develop into an embryo and the ovule becomes a seed

Question 5

summarize why the conifers have been so ecologically successful in certain environments, but not others

Answer 5

seeds have been favoured as they reduce water loss
pines are more resistant to the cold
pines can synthesize for longer
they grow slowly as gas exchange and nutrients are slow
overall evolutionary trade-offs explain why the conifers are so successful in some habitats, but not others

Question 6

Evolutionary trends in more advanced flowers

Answer 6

Changes in the number of parts
- Sepals or carpals lost

Fusion

Position of the ovary can change

Bilateral symmetry
- Only one plane
○ Insect has to enter in a certain and precise way

Question 7

asteraceae

Answer 7

have composite flowerheads each consisting of many individual flowers (capitulum)

primarily use animal pollination

Question 8

orchidaceae

Answer 8

have bilateral symmetry
contains reproductive organs (stamen, pistol and modified sepals an petals)
ovules are minute
nectar is produced in the stem
the pollinator is in coevolution with the flowers
use insect, bird and self pollination

Question 8

what are the reproductive structures of angiosperms

Answer 8

flowers

Question 8

• explain how diversity has been greatly enhanced in the angiosperms due to coevolutionary interactions with pollinators, as well as impacts of pathogens, herbivores and humans (e.g., artificial selection)

Answer 8

development of floral traits, and pollinators have coevolved behaviours

pathogens exert pressure for angiosperms to develop defence mechanisms

human activities
agriculture, horticulture and breeding programs have led to the enhancement of diversity through artificial selection

Question 8

ways in which seed dispersal is diverse

Answer 8

water, wind, animals

Question 9

Epiphyte

Answer 9

• Plants that live on the surface of other plants
  
  • Such as an orchid

Question 10

3 F’s of the Angiosperm cycle

Answer 10

Flowers
Fertilization is a double event (2 sperm that will join with two female gametes)
Fruit - production of fruit around the seed

Question 11

male gametophyte development angiosperms

Answer 11

microsporocyte is diploid
microspores are haploid
4 microspores, turn into germinative cell via mitosis (will form 2 sperm)

Question 12

female gametophyte development angiosperms

Answer 12

megasporangium, megasporocytes and integuments are all diploid - make 4 megaspores from meiosis

the surviving megaspore, antipodal cells (3), polar nuclei (2), egg (1) and synergids (2) are all haploid
ovules are diploid

3 sets of mitosis gives rise to 8 different cells
one egg
2 polar nuclei
around that are the support cells

Question 13

significance of the two fertilization events in angiosperms

Answer 13

Pollen tube releases two sperm, one fertilizes egg and the other joins the polar nuclei to form a 3n tissue - triploid
-this endosperm forms the nutrient tissue that will feed the seed

Double fertilization is about timing
Doesn’t waste resources in case no progeny is available
Two sperm have to come in at the same time

Question 14

evaluate the evolutionary fitness advantages of angiosperms compared to gymnosperms

Answer 14

more rapid - female gamete maturation doesn’t take as long

more efficient resource use: double fertilization ensures endosperm isnt developed if the egg is not fertilized

carpal: provides protection, dispersal mechanisms,

pollination by animals improves transfers

Question 14

Apomixis

Answer 14

Diploid cell just goes ahead and produces the seed without the need for fertilization