What is the cell theory?
Are turtles endangered?
Worldwide turtle populations have declined due to several reasons, including habitat destruction; exploitation of species by humans for their eggs, leather, and meat; and their becoming accidentally caught in the nets of fishermen. In particular danger are sea turtles, such as Kemp’s ridley sea turtle (Lepidochelys kempii), which is believed to have a population of only a few hundred. Other species include the Central American river turtle (Dermatemys mawii), the green sea turtle (Chelonia mydas), and the leatherback sea turtle (Dermochelys coriacea). Endangered tortoises include the angulated tortoise (Geochelone yniphora), the desert tortoise (Gopherus agassizii), and the Galapagos tortoise (Geochelone elephantopus).
What is a dolphin-safe tuna?
The order Cetacea, composed of whales, dolphins, and porpoises, were spared from the extinction of large mammals at the end of the Pleistocene about 10,000 years ago. The twentieth century, with its many technological improvements, was the most destructive period for the Cetacea. In 1972, the U.S. Congress passed the Marine Mammal Protection Act; one of its goals was to reduce the number of small cetaceans (notably Stenalla and Delphinus) killed and injured during commercial fishing operations, such as the incidental catch of dolphins in tuna purse-seines (nets that close up to form a huge ball to be hoisted aboard a ship).
What is the current population and status of the great whales?
Dolphins are often found swimming with schools of yellowfin tuna and are caught along with the tuna by fisherman who use purse-seine nets. The dolphins are drowned by this fishing method because they must be able to breathe air to survive. The Earth Island Institute established five standards in order for tuna to be considered “dolphin safe”. They are:
- No intentional chasing, netting, or encirclement of dolphins during an entire tuna fishing trip
- No use of drift gill nets to catch tuna
- No accidental killing or serious injury to any dolphins during net sets
- No mixing of dolphin-safe and dolphin-deadly tuna in individual boat wells (for accidental kill of dolphins), or in processing or storage facilities
- Each trip in the Eastern Tropical Pacific Ocean (ETP) by vessels 400 gross tons and above must have an independent observer onboard attesting to the compliance with points (1) through (4) above
More than 90 percent of the world’s tuna companies adhere to these standards.
The cell theory is the concept that all living things are made up of essential units called “cells.” The cell is the simplest collection of matter that can live. There are diverse forms of life existing as single-celled organisms. More complex organisms, including plants and animals, are multicellular—cooperatives of many kinds of specialized cells that could not survive for long on their own. All cells come from preexisting cells and are related by division to earlier cells that have been modified in various ways during the long evolutionary history of life on Earth. Everything an organism does occurs fundamentally at the cellular level.