Plants

Characteristics of Plants

• Cell structure is different, such as the cell wall giving cells a particular shape.
• Photosynthesis through chloroplasts.
• Plants are autotrophic meaning they can create their own energy from sunlight.
• Plants are sessile and don't move around.
• Plants store energy as carbohydrates as they don't need the weight efficiency of lipids.
• Plants can reproduce both sexually and asexually.
• Sexual reproduction through spores or seeds.
• Plants are most recognizable from their structure and their mechanisms of reproduction.

The Beginning

• The first photosynthetic organisms where single-celled, water-living organisms.
• These cells were most notable for being able to do photosynthesis.
• Cyanobacteria were the first organisms to photosynthesize.
• Multicellular algae began to develop.
• Being multicellular allowed for specialized cells.

Plants on Land

• The first plants on land were similar to modern mosses.
• They had no vascular tissue, roots, stems or leaves.
• They were still multicellular organisms and they likely lived on damp, shady environments.
• Males and females were separate plant (most modern plants have both female and male reproductive organs for context).
• These were called bryophytes.

Vascular Plants

• An example of vascular plants are Filicinophytes, or ferns.
• Plants began to develop vascular structures allowing them to grow taller and compete for light.
• The xylem moves water up from the ground to the leaves and the phloem moves carbohydrates down to grow the roots and stem.
• The first vascular plants only had spores, meaning that fertilization required moisture.
• Some modern plants reproduce with spores, such as ferns, horsetails and clubmosses.

Reproduction of Ferns

• Alternations of diploid and haploid generations.
• Haploid spores are released into the environment and develop into gametophytes.
• The gametophytes from males and females turn into gametes that can be fertilized in a moist environment.
• The gamete can then grow and develops sporangia underneath its leaves when mature.
• Spores are formed inside the sporangia and are released for mating.

Production of Seeds

• The embryo can develop independently from the parent plant and environment.
• The seed can grow from the food inside of the seed.
• Seeds are fertilized through pollen which spreads through the air like spores but doesn't require moisture for fertilization.
  
• Seeds provide nourishment for the embryo.
• They have an endosperm made of lots of proteins, oils and starches.
• The seeds are protected by the seed coat.
  
• Seeds can last a very long time, sometimes for thousands of years.
• They can survive until they are met by suitable conditions, which is when they emerge.

Dispersal Methods

• Seeds have a variety of dispersal methods, such as wind, water and animals.
• Dispersal through animals is called zoochory.
• Dispersal by wind is called anemochory.
• Dispersal by water is called hydrochory.

Flowering Plants

• Flowers, endosperm with seeds and fruit.
• They are also called angiosperms.
• The flowers can be pollinated and by other animals and the pollen for flowering plants.
• The most diverse group of plants today. They make up about 80% of all known extant plant species.
• The main function of a flower is to produce seeds.
• Shape and coloring is to lure in pollinators.
• Flowering plants share a coevolution with insects.
• The insects get nectar when they pollinate the flowers.

Pollination Methods

Cross-Pollination

• Pollen from one individual fertilizes pistil from another plant.
• This sexual reproduction leads to diversity.
• Insects, birds and animals transfer the pollen.

Self-Pollination

• Self-pollination is when pollen fertilizes the pistil from the same plant.
• This isn't good for genetic diversity and is generally avoided.
• There might be different timing for maturation of female and male parts.
• Male and female plants might be different plants. This is called dioecy.

Mesozoic Plants

• Gingko biloba is the only remaining tree from the Gingko family, which developed in the Jurassic era.
• Flowering plants (angiosperms) emerged and formed a coevolution with insects.
• This led to rapid diversification of insects and flowering plants.
• Insects recovered since their mass extinction in the Permian extinction.