Study Notes on Gymnosperms and Angiosperms
Bristlecone Pine:
Some bristlecone pines are over 4,000 years old.
They were saplings when the pyramids were being constructed.
Adaptations of Gymnosperms:
Three main adaptations for survival in dry habitats:
Reduction of the gametophyte size.
Advent of pollen and seeds.
Gametophyte vs Sporophyte:
In bryophytes (mosses), the gametophyte is larger than the sporophyte.
In ferns (seedless vascular plants), the sporophyte is larger than the gametophyte.
In gymnosperms app L, with the gametophyte being significantly reduced.
Life Cycle of Gymnosperms:
Typical gymnosperms have two types of cones:
Female cones (seed-producing).
Male cones (pollen-producing).
Male gametophytes (pollen) are wind-dispersed.
The female gametophyte is retained within the ovaries (ovules) of the cones.
Pollen and Fertilization:
Pollen grains are microscopic and containing two sperm cells.
Wind pollination is the main method for gymnosperms, requiring the production of a large amount of pollen.
After successful pollination, a pollen tube grows to fertilize the egg.
Seed Development:
Seeds develop from fertilized ovules, containing:
An embryo (the developing plant).
An endosperm (nutritional supply).
Seeds provide advantages for survival, enabling reproduction without the dependency on water.
Angiosperms (Flowering Plants):
Represent over 250,000 species with potential estimates exceeding 500,000.
Characterized by efficient vascular tissues and flowers, often used to attract pollinators.
Pollinators include insects, birds, and bats.
Flower Structure and Function:
A flower comprises various parts:
Sepals: green protective outer covering.
Petals: often colorful to attract pollinators.
Stamens: male structure producing pollen, containing anthers.
Carpel: the female structure containing the ovary and ovules.
Ovules: develop into seeds after fertilization.
Fruit Formation:
After fertilization, the ovary develops into a fruit, protecting the seeds and aiding in their dispersal.
Fruits can be a nutrient source for animals, which helps in seed dispersion.
Different fruits have different strategies for seed number based on the number of ovules fertilized.
Pollination Mechanisms:
Brightly colored flowers often attract birds; yellow and other colors attract insects.
Some flowers are adapted for night pollinators and have special features for visibility.
Seed Dispersal Strategies:
Seed dispersal mechanisms include wind and animal-mediated dispersal (e.g., fruit consumption).
Some seeds have adaptations (like hooks or sticky surfaces) to attach to animal fur or clothing.
Fungi:
Important decomposers, along with bacteria, recycle nutrients in ecosystems.
Fungi have a body structure made of hyphae; the mass of hyphae forms mycelium.
They absorb nutrients by secreting enzymes to break down organic material, relying on their unique cell wall component, chitin, which is also found in the exoskeletons of insects.
Fungal Reproduction:
Can occur sexually or asexually through spore production.
Spores are dispersed widely and can germinate in suitable conditions.
Human Interactions with Flowers and Plants:
Flowers have significant agricultural and ecological importance, directly impacting food and resources available to humans.
Selective breeding in agriculture aims to produce larger, sweeter fruits for consumption.
Note on Allergies:
Pollen can cause allergies (hay fever) as an immune response to inhaled pollen.
General Importance of Gymnosperms and Angiosperms:
Gymnosperms provide timber and paper products.
Angiosperms supply the majority of food resources for humans and livestock.