Define heliophytes and sciophytes. Name a plant from your locality that is either heliophyte or sciophyte.
Plants growing well in bright sunlight or favour bright light are called heliophytes or sun plants. While those plants which require low intensity of light or partial shade for growing are termed as shade loving plants or sciophytes.
Why do submerged plants receive weaker illumination than exposed floating plants in a lake?
Submerged plants receive weaker illumination than exposed floating plants in a lake because all colours of the visible components of the spectrum of light do not enter or penetrate in the depths of water.
In a sea shore, the benthic animals live in sandy, muddy and rocky substrata and accordingly developed the following adaptations.
(a) Burrowing
(b) Building cubes
(c) Holdfasts/peduncle
Find the suitable substratum against each adaptation.
In a sea shore, water current restrict distribution of organisms. In streamed areas of ocean, animals are strong swimmer or possess attaching organs such as peduncle, or live under stone, in burrows etc.
Burrowing animals like tubeworm, Nerlies are strong swimmer. Burrowing, building cubes and holdfast or penduncle adaptation are found in sandy, muddy and rocky substratum respectively.
Categorise the following plants into hydrophytes, halophytes, mesophytes and xerophytes. Give reasons for your answers.
(a) Salvinia
(b) Opuntia
(c) Rhizophora
(d) Mangifera
(a) Salvinia is a hydrophytes - Partially or completly submerged in water.
(b) Opuntia is a xerophyte - Dry habitat succulent leaves.
(c) Rhizophora is a halophyte - Saline habitat
(d) Mangifera is a mesophyte - Terrestrial habitat.
In a pond, we see plants which are free-floating; rooted-submerged, rooted emergent rooted with floating leaves. Write the type of plants against each of them.
$$ \begin{array}{ll|l} \hline & \text { Plant Name } & \text { Type } \\ \hline \text { (a) } & \text { Hydrilla } & \\ \text { (b) } & \text { Typha } & \\ \text { (c) } & \text { Nymphaea } & \\ \text { (d) } & \text { Lemna } & \\ \text { (e) } & \text { Vallisneria } & \\ \hline \end{array} $$(a) Hydrilla is submerged hydrophyte
(b) Typha is rooted emergent
(c) Nymphaea is rooted with floating leaves
(d) Lemna is free floating hydrophyte
(e) Vallisnaria is rooted submerged hydrophytes.