Topic 17: Seed Plants - Angiosperms Flashcards
Angiosperms
Produce flowers and fruits, most diverse group of plants
What are the two Shared Derived Traits of Angiosperms (3Fs)
Flowers, Double Fertilization, and Fruits
What is the Angio Life Cycle?
Diploid sporophytes produce spores by meiosis, which grows into haploid gametophytes. These produce haploid gametes by mitosis, forming a diploid sporophyte through fertilization.
What are flowers made for?
Sexual reproduction
What are the four types of modified leaves of flowers?
- Sepals
- Petals
- Stamens
- Carpels
Sepals
They are sterile and enclose/protect flowers.
Petals
Sterile; are brightly coloured to attract pollinators.
Stamens
Reproductive organ responsible for producing spores. Consists of a stalk (filament) topped by an anther containing pollen sacs that produce pollen. (Male)
Pollen Sacs
Microsporangia
Carpel
Reproductive organ responsible for producing the ovule. Consists of an ovary at the base, and a style leading up to the stigma, where pollen is received.
Clusters of flowers
Inflorescences ex. sunflowers.
Generative cell
develops into sperm nuclei
Tube cell
forms the pollen tube.
Polar nuclei
large central cell in female gametophytes contains two nuclei known as this.
How many megaspores are produced?
4 but only one survives
What happens when megaspores divide?
Produces 7-celled female gametophyte.
Pollination
The transfer of pollen from an anther to a stigma.
Double Fertilization
When the pollen tube discharges two sperm nuclie into the female gametophye one fertilizes the egg, while the other combines with two polar nuclei; forming a triploid cell.
What happens to the triploid cell?
Develops into endosperm: a tissue rich in nutrients that nourish the embryo.
2 Steps Post-Fertilization
1) Fertilized ovule develops into a seed
2) Ovary develops into a fruit enclosing the seeds
What does the endosperm do?
Undergoes round of mitosis to generate food for the embryo.
Fruit Development
The sporophyte ovary walls thicken and mature.
What is the function of fruit?
1) to protect the seed when immature by being unappealing
2) to assist in seed dispersal by being appealing.
What are the two categories of fruit?
Dry and Fleshy
4 Adaptive Advantages of Angiosperm Fertilization
- Endosperm develops after double fertilization (Conservation)
- Fruit development is initiated by fertilization (efficiency)
- Size reduction of female gametophyte (min. resources)
- Rapid development of female development
Modes of Pollination
Abiotic and Biotic
Coevolution of Flowers and Pollinators
Species influence the evolution of interacting species in response to the selection pressures.
Example of Coevolution
Darwin’s Orchids and hawk-moth tongues.
Sexual Reproduction
Meiosis and fertilization, yielding genetic diverse offspring.
Asexual Reproduction
Generates genetically identical clones.
Fragmentation
Where the parent plant separates into parts with each fragment developing into a new plant
Apomixis
From a diploid cell without fertilization
Advantage and Disadvantage of Asexual
Rapid growth, genetically vulnerable
Advantage and Disadvantage of Sexual
Increase gene diversity, high risk in seeding stage.
3 Ways to Prevent Self-Fertilization
- Self Incompatibility
- Incomplete Flowers ( separate flowers w/ separate genders)
- Temporal/Spatial Separation
When is self-fertilization beneficial?
When plants are in isolated environments, or pollinators are rare.
When did angiosperms start dominating Earth?
In the Cretaceous period.
Why did angiosperms begin to dominate?
- Developed modified xylem vessels
- Rapid speciation due to coevolution
- Rapid reproduction compared to gymno
Amborella
Basal extant species of angiosperms
Eudicots (dicots)
Contain an embryo w/ embryonic axis attached to two cotyledons
Cotyledons
Means seedling leaves
Monocot
have one cotyledon and a large endosperm
