Why are plants important to the ecosystem?
- primary producers
- convert sunlight into chemical energy that other organisms can ingest and use (perform photosynthesis)
- carbon cycle - turning CO2 into sugars
- nitrogen, mineral & nutrient cycling
- remove toxins from soil (detoxify)
- use plants for food, shelter, fuel, fibre, and medicines (aspirin, quinine (malaria), morphine - produces oxygen
- purify water and air
How do plants grow?
- optimal amounts of water
- minerals
- nutrients
- soil
- sunlight
- warmth
- gases (oxygen and carbon dioxide)
Characteristics of plants
- eukaryotic organisms
- have a cell wall that contain the carbohydrate cellulose
- carry out photosynthesis using the pigment chlorophyll to turn sunlight into chemical energy
- photoautotrophs
Adaptations
(for plants)
- formation of embryo, a reproductive structure that develops into a plant
- the ability to grow and stand tall to get as much as sunlight as possible
- tissues to transport waste, nutrients, and water
- strategies to reproduce water loss
- strategies to disperse reproductive structures without water currents
Alternation of generations
most plants life cycle alternates between haploid and diploid
Haploid Generation
gametophyte : produces eggs and sperm cells (gametes)
when gametes fuse, it produces diploid zygote which then develops into an embryo
Diploid Generation
sporophyte : produces spores
Gametes vs Spores
- spores can reproduce without having to fuse with another cell.
- spores of some plants have tough coats that allows them to resist harsh environments
- gametes aren’t adapted to harsh
conditions
Plant Evolution
Evolutionary Steps (4)
Evolutionary steps for plants:
1. plants without leaves, stems, seeds colonize areas where water and land meet. (mosses)
2. plants develop lignin and begin to stand up right - lignin is chemicals that hardens cell wall, they also develop vascular tissue, to transport water and nutrients. (ferns)
3. development of seeds - embryos covered in protective covering along with a food supply, allowing plants to spread without drying out (seed plants)
4. flowering plants - reproductive strucutre that attracts animals to help spread seeds (flowering plants)
Major Groups of Plants
- Green Algae
- mosses and relatives
- ferns and relatives
- seed plants
- flowering plants
Green Algae
Major Group of Plants
- biologists classified them in the protista kingdom but evidence has shown that they have cell walls and photosynthethic pigments identical to plants
- do not undergo alternation of generations
- closest relatives of plant ancestors
- found in shallow freshwater around edges of ponds and lakes
Mosses and Relatives
Major Group of Plants
- are **byrophytes ** (first land plant)
- grow near damp locations where they can obtain water easily
- does not have seeds, stems, or rigid support structures (can’t grow tall, called non-vascular)
- can withstand long dry periods and harsh tundra-like conditions
- gametophyte is the dominant generation
- male and female gametes are produced in separate reproductive structures
- sperm are flagellated and must swim
through water to eggs
- sperm are flagellated and must swim
Ferns and Relatives
Major Group of Plants
- sporophyte is the dominant generation (brown dots on the underside of ferns are made up of spore capsules)
- each capsules releases a large amount of tiny haploid spores that drift to the ground and grow into tiny gametophytes on or below the soil surface
- gametophyte produces eggs and flagellated sperm
- sperm are flagellated and must swim through water to fertilize eggs
Seed Plants
Major Group of Plants
- gymnosperms : not protected and enclosed in an ovary
- vascular plants with seeds
- seeds are plant embryos packaged in a protective coat along with a food supply
- two adaptations for survival in diverse land habitats:
- smaller gametophytes than fern, can live on their own without the protection of larger sporophytes
- pollen evolution allowed sperms to reach eggs by travelling through a dry environment instead of swimming through water.
Flowering Plants
angiosperm = enclosed seed
- have structures that prevent water loss
- improve their ability to reproduce on land
- flowers are the most effective reproductive and seed dispersal structures found in the plant kingdom
- have many adaptations that attract insects/other animals to transfer pollen directly from one flower to another
pollinated flowers –> ripened ovary –> fruit
How are fruits an effective way to disperse seeds?
Flowering Plants
- attract animals and ingest them
- if undigested, seeds are passed through animals unharmed landing in new locations
What is transpiration?
the release of water through the leaves (water from the ground is moved into the atmosphere)
