Seeds, Adaptation & Plant Evolution

Seeds and Plant Evolution

• Seeds changed plant evolution
• Seed evolution has been an effect, not a cause
• Natural selection isn't a direct cause-and-effect
• Seeds enabled the evolution of terrestrial plant ecosystems

Plant Adaptation to Land

• Plants moved to land for available resources
• Plant adaptation to land is exemplified by the seed
• A seed contains a baby, embryo and nutrients surrounded by a protective coat genetically modified from the previous plant
• Gametophytes are reduced in seed plants
• Gamete heterospory is common in seed plants
• Ovules and pollen contribute to the production of terrestrial life

Plant Group Evolution

• Gymnosperms and angiosperms are unique plant groupings.
• Seed plants are divided into gymnosperms and angiosperms.
• Gymnosperms appeared early in the fossil record
• Sperm types determined better suitability of plants to drier conditions
• Angiosperms evolved later from general sperms
• Ancestors of seed plants were likely homosporous
• Seed plants are generally heterosporous but not absolute.

Megaspores and Microspores

• Megasporangia produces megaspores that produce the female gametophytes of the seed.
• Microsporangia produce microspores that give rise to the male gametophytes or the sperm (pollen).
• A megasporangium contains food and nourishment for the developing embryo.
• The megaspore supplies nourishment after meeting the microspore.
• Pollination and fertilization are different.
• Pollination is when pollen comes together
• Fertilization is when n becomes n+n
• Seeds evolved to provide evolutionary advantages
• Seeds can stay dormant for a long time, be buried, or be eaten and dispersed
• Seeds dispersed by animals aid in adaptation to the terrestrial environment.

Gymnosperm Reproduction

• Gymnosperms have naked seeds, not enclosed by ovaries (fruits).
• Four groups of gymnosperms: Cycads, Ginkgo biloba, Gnetales, and Conifers.
• Gymnosperms thrived during the Mesozoic era.
• Relatively few species exist today due to competition
• Dinosaurs consumed gymnosperms during dinosaur times

Gymnosperm Sperm

• Multi-flagellated sperm are present in some gymnosperms
• Insects play a part in pollinating geminal sperms
• Plants transfer pollen when they eat the pollen
• Pollination became widely developed with angiosperms

Conifers

• Conifers have adapted to conserve moisture, allowing survival in dry conditions.
• Foliage is modified in conifers for water conservation
• Conifers have special adaptations, such as needles, coated for winter weather
• Conifers use windblown seeds for offspring dispersal, but it may also be carried by animals and floods
• Heterosporous plants have separate male and female parts of the flower.

Glaciers and Gymnosperm

• The surface of glacial alps is younger than material underneath due to glacial carving
• Bristlecone pines live for thousands of years, and are incredibly aging
• Some trees have been unchanged since the Jurassic period

Conifer Life Cycle and Reproduction

• Conifers are replanted after being cut down
• Some gymnosperms don't maintain leaf structure for photosynthesis
• Pioneers often misidentified trees
• Native Americans made pemmican using Juniper berries
• The sporophyte supports the gametophytes
• Cones produce the babies via meiosis, and they produce pollen grains
• Pollen grains go through meiosis and move into the micropyle for pollination

Seed dispersal

• Ovules are contained in the sporophyte cones
• The development of the baby plant (fertilization) is started biochemically by the pollen attaching to the micropile
• Seeds provide food for the baby plant
• Naked seeds don't have fruit, so they rely on coatings for this
• Seeds get planted when they fall near the tree, or vector carries them a distance away

Seed Survival

• Seeds are dispersed by animals that eat them.
• Seeds are dispersed by other environmental factors, such as wind and water

Plant Genetics

• Pando is what the Aspen tree colonies are know as Pando - Aspen tree colonies: a singular organism

Angiosperms - Flowering Plants

• Angiosperms have ovaries, which produce fruits
• Flowers and fruit are reproductive adaptations of angiosperms
• Flowers: reproductive structures that produce petals, sepals, and other parts
• Angiosperms evolved from gymnosperms, and are successful due to rapid and effective reproduction
• Animals and insects pollinate many angiosperm species
• Other angiosperms make use of water
• Angiosperms have a flower; a specialized shoot with 4 types of modified leaves
• Sepals protect the flower while it develops.
• Petals attract pollinators.
• Stamens produce pollen on their terminal anthers. A carpal consists of an ovary
• Pollen is received.
• Fruit derives from a mature ovary, and it provides nursery to the babies.
• Fruits can contain other flower parts.

Seed Survival Strategy

• Fruit protects seeds and aids in their dispersal.
• Some seed coats needed protection to go through the digestive tract, and need resistant digestive enzymes
• Seed coats withstand the low pH or digestive enzymes in the acidity in the stomach
• Some seeds need disruption of the seed coat in order to germinate; scarification or scraping

Learn about the role of seeds in plant evolution and adaptation to terrestrial environments. Explore gametophyte reduction, gamete heterospory, and the significance of ovules and pollen. Discover the evolutionary paths of gymnosperms and angiosperms, highlighting sperm types and adaptations to drier conditions.