Lecture 13: Gymnosperms Flashcards
Define homosporous and heterosporous.
Homosporous: plants where a single type of spore develops into a bisexual gamete
Heterosporous: plants in which the sporophyte produces two types of spores that differ in size and develop into male or female
What are the three major innovations of gymnosperms relative to seedless vascular plants?
- Much reduced size and complexity of the gametophyte. The gametophyte is no longer free living
- A shift from motile to non-motile male gametes. Water is no longer needed
- Evolution of the seed, which is an embryo othe sporophyte in a protective package that nicludes a food supply.
Gymnosperms are called ‘naked seed’ since their seed is not in a fruit
What are the five major groups of gymnosperms?
- Cycadophyta
- Gingkophyta
- Pinophyta
- Gnetophytes
- ????
Define these terms associated with the pine life-cycle
Microsporangia
Megasporangia
Megaspore
Microspore
Heterosporous
Ovule
Pollen
Microsporangia: Where meiosis occurs to produce male spores
- Megasporangia: where meiosis occurs to produce female spores
- mega spore: female spore
- microspore: male spore
- Heterosporous: two types of spores
- Ovule: a structure that contains the female gametophyte
- Pollen: an immature male gametophyte
What replaced motile (swimming) sperm in gymnosperms?
Wind born pollen. Pollen develops into the male gametophyte when they reach the female gametophyte.
Where is the fertilized zygote contained in pines?
What three things does the seed consist of?
It is contained within the megagametophyte and undergoes cell division to become the embryo.
The seed consists of:
- the seed coat, which is sporphytic tissue from the mother (diploid)
- the food reserves that are derives from the megagametophyte (haploid)
- the embryo, which is derived from the union of sperm and egg (diploid)
What are the four key features of the pine life-cycle?
- Heterosporous (mega and microspore)
- Fertilization is no longer dependent on water
- Female gametophyte is NOT free living, but is always attached to and protected by sporophytic tissue
- Seed protects and provides food for the sporophyte embryo. Gametophytic tissue spplies food while sporophytic tissue makes the seed coat
What are angiosperms?
Angiosperms have flowers, making them the most successful of the four groups of plants.
They are the most successful based on:
1. Numbers of species
2. Ecological diversity
3. Ascension in the fossil record
Define these terms in regards to the angiosperm flower
Petal
Anther
Filament
Stamen
Stigma
Style
Ovary
Carpel
Ovule
- Petal: modified leaves, usually colorful
- Anther: place of microspore production (pollen)
- Filament: a stalk that supports the anther
- Stamen: consists of anther and filament
- Stigma: sticky end that receives pollen
- Style: tube through which pollen tube must grow
- Ovary: contains the ovule, protects the ovule, develops into fruit
- Carpel: consists of the stigma, style and ovary
- Ovule: contains megagametophyte
What are the three differences between the gymnosperm and angiosperm life cycles?
- The megagametophyte is even more reduced in angiosperms.
- Angiosperms undergo double fertilization. This is where two sperm fertilize cells in the ovule, one fertilizes the egg and the other fuses with two haploid nuclei resulting in a 3n tissue known as the endosperm.
- When the ovule develops into the seed, the ovary develops into the fruit. The fruit is the mature ovary of a flower that protects dormant seeds and aids in seed dispersal.
Why have angiosperms been so successful? (4)
- There has been continued improvement of morphological structures, such as vascular tissue. So, angiosperms are more water efficient.
- Angiosperms are capable of more rapid maturation than gymnosperms
- Diversity of pollination. Angiosperms can be pollinated by more than wind, such as water and animals.
- Fruit attracts animals who eat the fruit and diseperse the seed in their feces. Feces can also represent excellent starting conditions for seed germination.
