Plant Biodiversity and Adaptation

Running head: Plant Biodiversity and Adaptation
Assignment
Biology II Week 1 Project
Plant Biodiversity and Adaptation
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Plant Biodiversity and Adaptation 2
Plant Biodiversity and Adaptation
There are significant evidences that earlier land plants have originated from the aquatic habitats
(Annenberg Foundation, 2017). The protists known as single celled freshwater green algae
(charophytes), evolved into a new form of terrestrial eukaryotic plants diversifying into four
subgroups namely mosses, ferns, conifers and flowering plants. These four subgroups are known
to exhibit a certain evolutionary pattern depicting the transition from water to land. The algae
still exhibit similarities with the plants like both have green pigment and both have cellulose in
cell walls.
Challenges faced by Plants during Transition
Body Support
The transition involved many challenges in their adaptations. For example, the body structure of
aquatic plants consisted of gas filled vesicles and kelps which provided them features to float on
the water. Under the water the plants had to face lower levels of gravitational forces. On the
other hand the land plants had to counter the force of gravity while getting taller. The adaptive
organelles like cell walls, and woody tissue provided support to the growing flowering plants and
conifers. Mosses do not possess any supportive woody tissues therefore exhibit only lower level
of growth on the land. The ferns have primitive tissue support confining their growth to just less
than a meter over the grounds.
Differentiation of Tissues

Plant Biodiversity and Adaptation 3
During the evolution of land adaptations in plants, tube like conducting vessels (xylem and
phloem) emerged to take the water and minerals up and down. The different parts of plants
exhibited differentiation where the leaves conducted the functions of making food, well
developed root system used to uptake nutrients from the soil, and the stem used to support the
plants structure (CK-12 Foundation, 2019). The aquatic plants used to take the nutrients directly
from the water through their surface. Such tissue differentiation was an evolutionary adaptation
in the plants to serve the diverse set of roles like making food, transporting it, and growing taller
on land habitat.
Earlier aquatic plants had a waxy layer named cuticle, to protect them under water and avoid te
loss of water from pant body. In land plants, the stomata evolved in the leaves to carry out the
gaseous exchange and water exchange.
Fertilization
In aquatic plants the transfer of pollen occurred through water. While in land adaptations, it
requires wind to transport the pollen and there is no need of water. In aquatic conditions, the
fertilized egg is always moist and never at risk of getting dehydrated while in land plants the
embryo are enclosed in seeds where it receives food for its development and growth. The
conifers and the flowering plants have seeds while the ferns and mosses rely on water for
dehydration of embryo and do not produce seeds.
The evolution of plants from aquatic to terrestrial habitats can be best represented by the plants
Mosses ( For example, Hygrohypnum styriacum)