Lecture 5A

Question 1

Components of the Genetic System (6)

Answer 1

• Sexual system
• Gene flow system
• Mating system
• Recombination system
• Reproductive system
• Adaptation system

Question 2

Sexual Systems (5)

Answer 2

• Sex Determination
• Types of Sexual Systems
• Sexual Structures
• Sexual Function
• Summary: Sexual Systems in Tropical Forests

Question 3

Fusion of two gametes to a zygote

Answer 3

SEXUAL SYSTEMS

Question 4

SEXUAL SYSTEMS

Answer 4

Fusion of two gametes to a zygote

Question 5

Determines the types of gametes produced by an individual (f,m,f/m,sterile)

Answer 5

Sexual types

Question 6

Sexual types

Answer 6

Determines the types of gametes produced by an individual (f,m,f/m,sterile)

Question 7

Dioecy

Answer 7

separate male and female

Question 8

Dioecy

Answer 8

separate male and
female

Question 9

male and female
organs in same
individual

Answer 9

Hermaphrodite

Question 10

Hermaphrodite

Answer 10

male and female
organs in same
individual

Question 11

Sexual systems in flowering plants
Diocey <- Hermaphrodite

Answer 11

Disruption of
self-incompatibility

Question 12

Disruption of
self-incompatibility

Answer 12

Diocey <- Hermaphrodite

Question 13

common in trees and in the tropics:

Answer 13

Dioecy

Question 14

prevent inbreeding depression when SI is broken

Answer 14

Dioecy

Question 15

Two forms of bisexuality:

Answer 15

Monoecy
Hermaphroditism

Question 16

Monoecy
Hermaphroditism

Answer 16

Two forms of bisexuality:

Question 17

male and female gametes
produced on the same plant but in
different flowers

Answer 17

Monoecy

Question 18

Monoecy

Answer 18

male and female gametes
produced on the same plant but in
different flowers

Question 19

male and female
gametes produced in a single flower

Answer 19

Hermaphroditism:

Question 20

Hermaphroditism:

Answer 20

male and female
gametes produced in a single flower

Question 21

Pollination possibilities in
hermaphroditic plants (4)

Answer 21

Autogamy
Allogamy
Geitonogamy
Xenogamy

Question 22

Autogamy
Allogamy
Geitonogamy
Xenogamy

Answer 22

Pollination possibilities in
hermaphroditic plants

Question 23

pollination with
pollen from the same
flower (selfing,
hermaphrodites)

Answer 23

Autogamy:

Question 24

Autogamy:

Answer 24

pollination with
pollen from the same
flower (selfing,
hermaphrodites)

Question 25

pollen transported from another flower

Answer 25

Allogamy

Question 26

Allogamy

Answer 26

pollen transported from another flower

Question 27

pollination
from different flower of
the same plant (selfing);
monoecious

Answer 27

Geitonogamy

Question 28

Geitonogamy

Answer 28

pollination
from different flower of
the same plant (selfing);
monoecious

Question 29

pollination
from other plants
(outcrossing); dioecious

Answer 29

Xenogamy

Question 30

Xenogamy

Answer 30

pollination
from other plants
(outcrossing); dioecious

Question 31

Sex determination in plants (5)

Answer 31

1. Plants are principally bisexual
2. But approx. 20% of flowering plants are dioecious
3. Sex chromosomes:
   
   • Rare, but described for some plants
     
     • Structurally different
     • Structurally identical i.e., spinach and asparagus
4. Sex determination for most plants unknown
   5.Some species are “sub-dioecious” – produce very rarely male and female gametes

Question 32

Pseudohermaphroditism in
Aucoumea klaineana (1-3-2)

Answer 32

1. Flowers complete, i.e. both stamen
   and pistil develop, but:
   
   • Two types of flowers:
     
     • Only stamen functionally active
     • Only pistil functionally active
   • Each tree produces only one
     type of flower, i.e. the species is
     functionally dioecious
   • “pseudohermaphroditism”:
     complete flower

Question 33

Sexual systems of Tropical Forest Plants (4)

Answer 33

1. Most plant have complete flowers, i.e., they are hermaphroditic - Often animal-pollinated
2. More than 20% are dioecious - particularly common for Salicaceae, Meliaceae, Ebenaceae
3. Few are monoecious - Often wind-pollinated
4. All other sexual systems are very rare

Question 34

Frequency of Dioecy (5)

Answer 34

1. Obligatory outcrossing (no selfing)
2. Evolution due to advantages of outcrossing, i.e. avoidance of selfing
3. Independent evolution in many tree families
4. More frequent in woody species than in herbaceous plants
5. Tropics are dominated by woody taxa: more dioecious species

Question 35

Sexual Structures (4-2)

Answer 35

1. Genetic structures
2. Frequency distribution of sexual types within populations
3. Meaningless, if only one type (e.g.
   hermaphroditism)
4. Dioecy:
   • Often unbalances sex ration
   • Excess of male plants more frequent than female excess

Question 36

Reasons for an Unbalanced Sex Ratio (7)

Answer 36

1. Mode of inheritance of sex (sex determination)
2. Gametic selection favoring one sex (pollen or ovules)
3. Resource allocation (female: seeds, energy? vs. male: pollen, vegetative energy: more male clones!)
4. Apomixis, asexual propagation
5. Early maturity of one sex (usually male rarely female)
6. Different frequency of flowering in m, f
7. Different survival of m, f