The eukaryotic kingdom known known as Chromista is composed of single celled organisms among which of all the algae containing chlorophyll a and c. Most of the species belonging to this group are also photosynthetic.
Due to the vast number of species, some Chromistas have an asexual reproduction, whereas other reproduce sexually.
Asexual reproduction is achieved by the process of cellular division known as mitosis in which a parent cell divides into two identical daughter cells.
Sexual reproduction occurs through flagellated zoospores. Male gamets are produced by the antheridia, the male sex organ of algae, ferns, fungi etc. The haploid female gamets are produced through mitosis in oogonia. The joining of two gamets is called syngamy.
Answer:
D. Calcium ions.
Explanation:
Here we are talking about the mechanism of muscle contraction. The most accepted theory of muscle contraction is sliding filament theory. It was given by Huxley and Huxley. During the process actin filaments slides over myosin filament by forming cross bridges. The sequence of events are as follows:
a. An action potential propagates through the motor nerve and reach the nerve endings on the muscle fiber at neuro-muscular junction.
b. Neurotransmitter called acetylcholine is released by the nerve endings.
c. Acetylcholine binds to the receptors on muscle fiber and opens the gated channels which causes flow of Na+ ions into the muscle fiber.
d. This influx of sodium ions initiates an action potential in the muscle fiber which reaches the T- tubules or transverse tubules. Here it causes the sarcoplasmic reticulum to release large amounts of calcium ion.
e. Calcium ions are responsible for initiating the attractive forces between actin and myosin filaments. Cross bridges are formed, actin slides over myosin causing the contraction of muscle.
The intermediate disturbance hypothesis predicts that communities with intermediate levels of disturbance will have the most diversity. If disturbances become too rare, competitive dominants will eliminate other species, reducing diversity as equilibrium conditions develop.
The intermediate disturbance hypothesis predicts that the highest levels of diversity will occur at moderate disturbance levels. We investigated the species diversity, abundance, and species diversity of bacteria on the human body in relation to washing disturbance. According to IDH theory, diversity is maximized at intermediate levels of disturbance because species that thrive at both early and late successional stages can coexist. The intermediate disturbance hypothesis (IDH) proposes that when ecological disturbance is neither too rare nor too frequent, local species diversity is maximized.
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