1. It is more complex and harmful.
2. It is a nitrogenous substance.
3. It is excreted through the excretory system.
4. It is not stored in the body.
5. It is not reused in the animal body.

The process by which nitrogenous waste products are regularly removed from the body is called excretion. Nitrogenous waste products are called excreta. The main excretory substances of the human body are urea, uric acid, ammonia, creatinine etc.

During the production of amino acid energy in the human body, some nitrogenous toxic waste products are produced. The main nitrogenous waste product of humans is urine. The main excretory organ is kidney. Kidney is called the master chemist of the body. 80% of excreta are excreted through the kidneys. The remaining 20% of the excreta is excreted through the accessory excretory organs. The auxiliary excretory organs in the human body are the skin, lungs, liver and digestive tract. The branch of biology that deals with the structure, function and diseases of kidney is called Nephrology.

Pteri absorb large amounts of arsenic from the soil. So it can be used to treat depression caused by arsenic.

Molecules of Lycopodium burn and emit colorful light. Hence it is called flint plant. Flint plant is used to make fireworks.

Ferns can be used to produce essential chemicals. Potash is obtained from Dryopteris and silicon from Equisetum. Potash is used to make soap and glass.

Fern plants are used in various events, home decoration, garden beautification etc. Lycopodium obscurum, also known as Christmas green, is used as a beautifier in Christmas celebrations. Lycopodium, Selaginella etc. are used for decoration.

(i) Lycopodium, Equisetum etc. are medicinal ferns. Homeopathic medicine is made from it.
(ii) Unani herbal medicines are prepared from ferns. These drugs are used in the treatment of ulcers, rheumatic fever, intestinal lesions etc.
(iii) Young stems of ferns are used as anthelmintics.
(iv) Marsilean obtained from Marsilea is used to treat neuralgia.
(v) Medicines for liver diseases are prepared from Selaginella botryoides.
(vi) Herba equisini medicine obtained from Equisetum arvense helps to treat blood purification and urinary tract diseases.
(vii) Medicine for gonorrhea is prepared from Equisetum debile.

1. Human food: Young leaves of Pteris are used as vegetable. The starchy stems and rhizomes of the fern are used as food. Kale and collard greens are favorite vegetables.
2. Animal Feed: Several species of Pteris are used as livestock feed. However, eating harmful and poisonous Pteris causes death of livestock. This is why Pteris is sometimes called a noxious and poisonous weed.
3. Fuel: Coal, oil and natural gas are obtained from the fossils of tree ferns which are used as fuel.
4. The medicine is ready
(i) Lycopodium, Equisetum etc. are medicinal ferns. Homeopathic medicine is made from it.
(ii) Unani herbal medicines are prepared from ferns. These drugs are used in the treatment of ulcers, rheumatic fever, intestinal lesions etc.
(iii) Young stems of ferns are used as anthelmintics.
(iv) Marsilean obtained from Marsilea is used to treat neuralgia.
(v) Medicines for liver diseases are prepared from Selaginella botryoides.
(vi) Herba equisini medicine obtained from Equisetum arvense helps to treat blood purification and urinary tract diseases.
(vii) Medicine for gonorrhea is prepared from Equisetum debile.
5. Beautification: Fern plants are used in various events, home decoration, garden beautification etc. Lycopodium obscurum, also known as Christmas green, is used as a beautifier in Christmas celebrations. Lycopodium, Selaginella etc. are used for decoration.
6. Production of chemicals: Ferns can be used to produce essential chemicals. Potash is obtained from Dryopteris and silicon from Equisetum. Potash is used to make soap and glass.
7. As Fertilizers: Some species of Terris are used as fertilizers on land.
8. Furniture Polish: Equisetum is used in wooden furniture polish.
9. Fireworks: Molecules of Lycopodium burn and emit colorful light. Hence it is called flint plant. Flint plant is used to make fireworks.
10. Antibiotics: Pteri absorb large amounts of arsenic from the soil. So it can be used to treat depression caused by arsenic.

The successive appearance of gametophyte and sporophyte stages in the life cycle of a plant is called generation. Pteris has two stages in its life cycle. Gametophyte state and sporophyte state.
1. Gametophyte stage: The stage of plant life cycle in which gametes i.e. sperm and egg are formed is called gametophyte stage. Spores are produced in sporophyte plants. Spore is the first cell of gametophyte. Spores germinate in favorable environment. The germinated spore divides by mitosis to form a green, flat and cordate prothallus. Fern prothallus is a gametophyte plant. Under its anterior groove the pitcher or flux-shaped female genital archegonia and below the thallus the round or ovoid male genital antheridia grow. Eggs are produced in the archegonium and spermatozoa in the antheridium. Sperm and egg unite to form zygote. The gametophyte phase ends with the formation of the zygote.
2. Sporophyte stage: The stage of plant life cycle in which spores are produced is called sporophyte stage. Gametophytes produce sperm and ovules in plants. A zygote is formed by the union of sperm and egg. Zygote is the first cell of sporophyte. The zygote becomes enveloped by the wall and becomes a zygospore. Zygospore germinates in favorable environment. The germinating zygospore divides repeatedly by the process of mitosis to form the sporophyte plant. The sorus grows on the leaf margin of the sporophyte. The sorus contains sporangia. Inside the sporangium is the spore mother cell. Each spore mother cell divides by meiosis to produce four spores. The sporophyte stage ends with the formation of spores.