Lecture 5: Terrestrial Plant Evolution Flashcards
(39 cards)
Define plants
Plants are eukaryotic, multicellular, photoautotrophic organisms that have cell walls made of cellulose.
How do plants distinguish from multicellular protists (algae)?
Algae (protists), like plants, can also eukaryotic, multicellular and photoautotrophic organisms that have cell walls.
But, the distinctions are that…
- ALL plants are multicellular, whereas algae can be uni or colonial.
- MOST plants live on LAND, whereas most algae live in aquatic or moist terrestrial habitats.
- ALL plants have a WAXY CUTICLE and STOMATA, whereas algae do not because algae are not in danger of desiccation due to their aquatic habitat and they are able to exchange gases through diffusion in the surrounding water.
- Most plants have ROOTS, STEMS, LEAVES and some have VASCULAR TISSUES, whereas algae do not because they are able to absorb all the nutrients and water their cells need from the surrounding aquatic environment.
What are the 5 basic resources required plants? Why are each needed?
Plants require: 1. Water 2. Light 3. CO2 all for photosynthesis
- O2 for cellular respiration
- Mineral nutrients for making proteins, DNA, fats, etc.
Describe vascular plants and provide an example
Plants that have vascular tissue systems that transport water and nutrients through the plant, as well as provide some structural support.
Ex. Gymnosperms like conifer trees
Describe non-vascular plants and provide an example
Plants that do not have vascular tissue systems. ex. Bryophytes like moss
How do algae function in the water?
- they are surrounded and supported by water (do not need internal structural support)
- they can only access sunlight near the surface
- absorb LIMITED dissolved O2, CO2, and nutrients directly from the water
- reproduce by releasing gametes directly into the water
What are 5 major challenges faced by the first terrestrial plants?
- Absorption of water and nutrients, the first terrestrial plants did not have roots (algae do not have roots) and they cannot obtain these through diffusion like they could in water
- reproduction would be more difficult due to the lack of water to disperse gametes into
- lack structural support
- transport of nutrients and water through the plant would be difficult
- dehydration or water loss - they would not have mechanisms to minimize water loss
What are 5 major challenges faced by the first terrestrial plants?
- Absorption of water and nutrients, the first terrestrial plants did not have roots (algae do not have roots) and they cannot obtain these through diffusion like they could in water
- reproduction would be more difficult due to the lack of water to disperse gametes into
- lack structural support
- transport of nutrients and water through the plant would be difficult
- dehydration or water loss - they would not have mechanisms to minimize water loss
define the term key adaptation
A trait that provides a new ability to exploit previously unavailable habitats or resources
Approximately how many years ago did plants colonize land?
475 million years ago
What are the first land plants called? When did they colonize land? Give an example of a group
The first land plants are called BRYOPHYTES and they colonized land approx. 475 mya.
An example is moss
What are the 2 key adaptations of bryophytes and how did they provide an advantage?
- Waxy cuticle: A waxy coating around the exterior of all land plants that functions to reduce water loss. This would reduce chances of dehydration and allow plants to inhabit regions further from water sources.
- Stomata: Pores in the surface of all land plants that open and close. The stomata allow for gas exchange to occur. This is advantageous because plants require CO2 and O2 for crucial life processes (photo. and CRt) and if the waxy cuticle blocks water, it will also block gas molecules.
What are the 2 key adaptations of bryophytes and how did they provide an advantage?
- Waxy cuticle: A waxy coating around the exterior of all land plants that functions to reduce water loss. This would reduce chances of dehydration and allow plants to inhabit regions further from water sources.
- Stomata: Pores in the surface of all land plants that open and close. The stomata allow for gas exchange to occur. This is advantageous because plants require CO2 and O2 for crucial life processes (photo. and CRt) and if the waxy cuticle blocks water, it will also block gas molecules.
What are the 2 main groups of plants?
Vascular and non-vascular
What are the 2 main groups of plants?
Vascular and non-vascular
Which group of plants are non-vascular?
Bryophytes
What are the 3 major limitations bryophytes (and non-vascular) plants face?
- Height limitations: because they have no vascular system and no true roots or leaves, they cannot transport nutrients or water long distances, they must remain close to the ground to increase contact AND limited structural support so they remain very small.
- They are restricted to at least periodically moist environments because they (like algae) require water for the dispersal of their gametes.
- Limited dispersal by spores. Spores can only travel short distances.
What are spores?
Single-celled reproductive units that explode out of reproductive structures
What are the second major group of plants to evolve on land called? What is an example? When did they evolve?
Seedless vascular plants evolved on land about 425 million years ago. An example is ferns.
When did seedless vascular plants evolve?
about 425 million years ago
What are the 3 seedless vascular plant key adaptations?
- Vascular tissue (xylem and phloem): tissues that connect throughout the plant and move water and nutrients long distances. The xylem provides a rigid secondary cell wall (made of lignin) that provides the plants with structural support against gravity.
- Leaves: are the main photosynthetic organ of these plants by increasing surface area for light capture.
- Roots: are structures that extend into the soil and increase access to water and mineral nutrients in the soil. Also provides anchorage to hold the plant in place.
All of these adaptations allowed these plants to grow taller and therefore become more competitive for resources like sunlight and mineral nutrients and space.
What are the 2 major limitations seedless vascular plants still face?
- Still limited to moist environments as their sperm still requires water to swim to the egg.
- Still produce spores, seedless means they do not produce seeds, but are still limited to dispersal by spores.
What are the third major group of plants to evolve on land? When did they evolve? Give an example.
Gymnosperms were the third group of plants to evolve on land and they evolved around 305 million years ago. An example of these are conifers.
What are the 2 major key advantages for gymnosperms?
- SEEDS: are an embryo (multicellular, unlike spores) surrounded with a food supply encased in a protective seed coating.
- POLLEN: is the reproductive structures in male plants (pollen is not sperm, but it produces sperm) that are transported to the female reproductive structure to produce sperm.
