Genus <i>Alexandreum</i> of dinoflagellates secretes neurotoxin saxitoxins which are the causative agents of paralytic shellfish poisoning (PSP). Molluscs such as mussels and clams feed on a large number of dinoflagellates, human consumption of those molluscs causes paralysis. 

Madness is a characteristic symptom of rabies which is caused by RNA virus “rabies virus” and is mostly spread through the bite of an infected dog. 

Syphilis is a sexually transmitted disease, caused by gram negative spirochete, <i>Treponema pallidum</i>. 

Plague is caused by gram negative rod shaped bacteria. <i>Yersinia pestis</i> and is characterised by flu-like symptoms. It is transmitted by bites from infected fleas. 

Hydrocolloids are the carbohydrates obtained from different species of algae.

Algin is a hydrocolloid which has good water holding capacity derived from brown algae (Phaeophyceae).

Agar is jelly like substance used in dairy toppings and other instant food products, derived from red algae (Rhodophyceae)

Bacteriophage : Virus infection bacteria are known as bacteriophage. (a) These are obligate parasites that occur in soil, sewage water, fruits.
(b) The phage possesses a tail and a head. .
© The viral DNA is thread like ds (double standed) macromolecule.
(d) There are 4 segments of the tail.
(e) Bacteriophage are of two types : (i) Lytic and (ii) Lysogenic phoges e.g., phage (Lambda), T2 phage etc.

The accumulation of large amounts of cell wall deposits left back by diatoms over billions of years is called diatomaceous earth.

1) CHLOROPHYCEAE also known as Green Algae.
    Major Pigments:- Chlorophyll a, chlorophyll b, Xanthophyll and Carotene.
    Food Stored:- Starch, Protein and Oil [Starch+Protein=Pyrenoid]

2) PHAEOPHYCEAE also know as Brown Algae.
    Major Pigments:- Chlorophyll a, Chlorophyll c, Fucoxanthin [Brown Colour].
    Food Stored:- Mannitol and Laminarin.

3) RHODOPHYCEAE also known as Red Algae.
    Major Pigments:- Chlorophyll a, Chlorophyll d, Phycoerythrin [Red Colour] and Phycocyanin [Blue Colour]
    Food Stored:- Floridean Starch

    
Two types of population growth patterns may occur depending on specific environmental conditions:

• An exponential growth pattern (J curve) occurs in an ideal, unlimited environment
• A logistic growth pattern (S curve) occurs when environmental pressures slow the rate of growth

Exponential Growth

• Exponential population growth will occur in an ideal environment where resources are unlimited
• In such an environment there will be no competition to place limits on a geometric rate of growth
• Initially population growth will be slow as there is a shortage of reproducing individuals that may be widely dispersed
• As population numbers increase the rate of growth similarly increases, resulting in an exponential (J-shaped) curve
• This maximal growth rate for a given population is known as its biotic potential
• Exponential growth can be seen in populations that are very small or in regions that are newly colonised by a species

Logistic Growth

• Logistic population growth will occur when population numbers begin to approach a finite carrying capacity
• The carrying capacity is the maximum number of a species that can be sustainably supported by the environment
• As a population approaches the carrying capacity, environmental resistance occurs, slowing the rate of growth
• This results in a sigmoidal (S-shaped) growth curve that plateaus at the carrying capacity (denoted by κ)
• Logistic growth will eventually be seen in any stable population occupying a fixed geographic space

The four whorls of a complete flower are:

First whorl: Calyx
Second whorl: Corolla
Third whorl: Androecium
Fourth whorl: Gynoecium

The compounds oxidised during the process of respiration are called as respiratory substrates. Carbohydrates, especially glucose, act as a respiratory substrate. Fats, proteins, and organic acids can also act as respiratory substrates depending upon the physiological condition of the body of an organism.

Phylum Arthropoda has almost a million species described to date. It accounts for 80% of known animal species. So phylum Arthropoda is the largest phylum in the animal kingdom. Several factors contributed to the success of arthropods especially the terrestrial arthropods as they adapted to solve the problems of support, stability, desiccation and respiration.

Lichens are the composite or dual organisms representing a symbiotic association between a fungus and alga. The fungal partner is called mycobiont whereas algal partner is called phycobiont. Algae prepares food for fungi and fungi provides shelter and absorbs mineral nutrient and water for its partner. Lichens grow on barren rocks, cooled volcanic lava and icy tundra soils. They can tolerate extreme dessication but not the polluted air.

Some of the characteristic features of viroids are given below-

• Viroids contain only RNA.
• These are known to be smaller in size and infect only the plants.
• These are among the smallest known agents causing infectious disease.
• Viroids are the species of nucleic acid with relatively low molecular weight and a unique structure.
• They reproduce within the host cell which they affect in and cause variations in them causing death.
• Viroids are mainly classified into two families namely Pospiviroidae- nuclear viroids and Avsunviroidae- chloroplastic viroids.
• Viroids are said to move in an intracellular manner, cell to cell through the plasmodesmata, and a long-distance through the phloem.

• Cilia and flagella are hair-like outgrowths of the cell membrane.
• Cilia and flagella help in cell movement.
• Core of cilia and flagella is called the axoneme, possesses a number of microtubules running parallel to the long axis.
• The axoneme usually has nine pairs of doublets of radially arranged peripheral microtubules, and a pair of centrally located microtubules. Such an arrangement of axonemal microtubules is referred to as the 9+2 array.
• The central tubules are connected by bridges and is also enclosed by a central sheath, which is connected to one of the tubules of each peripheral doublets by a radial spoke and hence there are nine radial spokes.
• The peripheral doublets are also interconnected by linkers.
• Both the cilium and flagellum emerge from centriole-like structure called the basal bodies.

(A) Phycomycetes- This group of fungi includes members such as Rhizopus, Albugo, etc.

(i) Mode of nutrition

They are obligate parasites on plants or are found on decaying matter such as wood.

(ii) Mode of reproduction

Asexual reproduction takes place through motile zoospores or non-motile aplanospores produced endogenously in sporangium.

Sexual reproduction may be of isogamous, anisogamous, or oogamous type resulting in the formation of thick-walled zygospore.

(B) Ascomycetes- This group of fungi includes members such as Penicillium, Aspergillus, Claviceps, and Neurospora.

(i) Mode of nutrition

They are sporophytic, decomposers, parasitic or coprophilous (growing on dung).

(ii) Mode of reproduction

Asexual reproduction occurs through asexual spores produced exogenously, such as conidia produced on conidiophores.

Sexual reproduction takes place through ascospores produced endogenously in sac-like asci and arranged inside ascocarps.

(C) Basidiomycetes- This group of fungi includes members such as Ustilago, Agaricus and Puccinia.

(i) Mode of nutrition

They grow as decomposers in soil or on logs and tree stumps. They also occur as parasites in plants causing diseases such as rusts and smuts.

(ii) Mode of reproduction

Asexual reproduction takes place commonly through fragmentation. Asexual spores are absent.

*** organs are absent but sexual reproduction takes place through plasmogamy. It involves fusion of two different strains of hyphae. The resulting dikaryon gives rise to a basidium. Four basidiospores are produced inside a basidium.

(D) Deuteromycetes – This group of fungi includes members such as Alternaria, Trichoderma, and Colletotrichum.

(i) Mode of nutrition

Some members are saprophytes while others are parasites. However, a large number act as decomposers of leaf litter.

(ii) Mode of reproduction

Asexual reproduction is the only way of reproduction in deuteromycetes. Which occurs through asexual spores called conidia.

Sexual reproduction is absent in deuteromycetes.

• We fall ill because we live in an area with polluted surroundings or lack of personal hygiene.

• It is very important to adopt certain strategies to stay healthy and prevent diseases.

• One should remain active by exercising daily.

ANGIOSPERMS

• In the angiosperms or flowering plants, the pollen grains and ovules are developed in specialized structures called flowers and the seeds are enclosed by fruits.
• They are divided into two classes
• The dicotyledons - characterized by having two cotyledons in their seeds.
• The monocotyledons- have only one cotyledon.

Euglena is a unicellular eukaryote. Euglena has characteristics of both plants and animals. Euglena is flagellated. Euglena has plastids and performs photosynthesis in light, but moves around in search of food using its flagellum at night. There are around 1000 species of Euglena found. They are found in freshwater, saltwater, marshes and also in moist soil.

Growth in biological terms is characteristic feature of all living organisms. It relates to increase in size by accumulation of protoplasm in the cell thus results in increase in size of the cell. Whereas increase in number in number of cell by cell division results is the size of individual organism.
Snow is an inanimate (non-living) object, while rolling over snow, it gathers more snow on its surface thus, it increases in size by physical phenomenon but not by biological phenomenon. So, this growth cannot be compared to that seen in living organisms.

Malpighian body is the part of a nephron in the kidney. It consists of its cup-shaped end together with the glomerulus that it encloses. The Malpighian body filtrates the blood and separates waste from the blood.