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Flashcards in Angiosperms Deck (54)
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1

How many species of angiosperm are there?

250 000

2

What are they important for?

Food source, Commercial products, Influence climate

3

What is a flower?

A feature specialised for sexual reproduction, a specialised shoot with modified sporpphyll

4

What are the sporophyte in angiosperms called?

Floral organs

5

What are the different floral organs?

Sepals, Petals, Stamen and carpel

6

What are the sepals?

Usually green and enclose the flower before it opens

7

What are the petals?

Brightly coloured to attract pollinators- not in wind pollinated plants,

8

Why are the petals and sepal sterile floral organs?

Not directly involved in reproduction

9

What is the role of the stamens?

Produce microspores that develop into pollen grains containing male gametophytes

10

How are the stamens structured?

Composed of a filamentous sac and the anther, where the pollen is produced

11

What is the role of the carpel?

Make megaspores and the female gametophytes, number is analogous, depends on species

12

How is the carpel structured?

At the tip is a sticky stigma that receives pollen. Style leads from the stigma to the ovary at the base of the carpel

13

What are the fruits?

Typically is a mature ovary

14

How does the fruit form?

Develops from ovules after fertilisation as the wall of the ovary thickens

15

What is the role of the fruit?

protect dormant seeds and aid in their dispersal

16

Where are the male gametophytes?

In the pollen

17

Where are the female gametophyte?

In the ovule

18

How is the pollen grain structured?

Two haploid cells, one is generative and develops into two sperm, the other is the tube cell

19

What happens when the pollen reached the stigma?

Pollen tube grows down style, sperm travel through micropyle - pore in the integument, and discharge into the female gametophyte

20

How does fertilisation occur?

One of the sperm will fertilise the egg, forming a diploid zygote, the other fuses with the two nuclei in the large central cell, producing a triploid cell

21

What is double fertilisation?

One fertilisation event produces a diploid embryo and a triploid cell - unique to angiosperms

22

What is the function of the triploid cell?

cell divides repeatedly and develops into the endosperm, which is a tissue rich in starch and other reserves that nourish the developing embryo

23

What is the function of double fertilisation?

Hypothesis is the it wouldn't be beneficial to develop endosperm and waste resources if the egg isn't fertilised, so is a way of conserving resources

24

What happens once the seed gets to a favourable environment?

Coat ruptures and embryo emerges as a seedling, using food stored in the endosperm and cotyledons

25

How is the female gametophyte produced?

Occurs in the ovary. meiosis occurs to form four haploid cells, only one survives, splits by mitosis to form 8 cells, 7 within a single embryo sac are accessory and polar cells for formation of the seed and one which is the egg

26

How is the mate gametophyte produced?

In the pollen, single diploid uncle splits by meiosis into four haploid cells, each become a pollen grain, then split again. Pollen grain consists of generative cell and tube cell

27

How did Angiosperms evolve?

Named the abominable mystery, not sure

28

When did the major branches of the clade diverge?

In the late mesozoic

29

When did they begin to dominate?

By mid cretaceous

30

What is the oldest fossil of angiosperms?

Archaefructus liaoningensis