Green Sea Turtle Chelonia mydas

Natural Selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in heritable traits of a population over time.

Natural selection is the process where organisms who are better adapted to their environment tend to survive and produce more offspring. Turtles roamed the earth more than 245 million years ago, they are part of the late triassic period. They adapted to eventually living in water the full time, to better their chance of survival. The green sea turtle evolved from eating insects and vegetation to algae, shrimp, and crabs. However, green sea turtles are mostly herbivorous. Some environmental pressures that might have caused these changes are

Variation is the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary.

The only variation between green sea turtles is the difference between shell color. Green sea turtle hatchlings have mostly black carapaces and light-colored plastrons. Carapaces of juveniles turn dark brown to olive, while those of mature adults are either entirely brown, spotted, or marbled with variegated rays. The turtle's plastron is hued yellow. The green sea turtles' limbs are dark-colored and lined with yellow, and are usually marked with a large dark brown spot in the center of each appendage.

Adaptation is a trait with a current functional role in the life of an organism that is maintained and evolved by means of natural selection

Green sea turtles have strong, paddle-like flippers that help them swim more efficiently and faster. The green sea turtle doesn't have a horned beak because the turtles grow up and become omnivorous. Also, the turtle adapted to become a bottom feeder. A green sea turtle can hold its breath underwater for up to five hours.

Speciation is the formation of new and distinct species in the course of evolution.

There are six other modern types of sea turtles: Leatherback, Hawksbill, Kemp's Ridley, Olive Ridley, Flatback, and Loggerhead.They derived from the Toxochelys, an extinct genus of marine turtle from the Cretaceous period. "Phylogenetic analysis shows that Toxochelys belong to an extinct lineage of turtles transitional between modern sea turtles and other turtles."

  • The Leatherback sea turtle grows the largest, dives the deepest, and travels the farthest of all sea turtles. The green sea turtle does not grow as large, dive as deep, and travel as far as the Leatherback turtle.
  • Hawksbill sea turtle's almost exclusively eat sponges. The Kemp's Ridley is the one of the smallest sea turtles weighing between 75 to 100 pounds. Their shells range in color from gray (in young turtles) to shades of olive green in adults. The Green Sea Turtle is herbivorous when it is young and becomes omnivorous as they grow older.
  • At around 7 to 15 years of age, the Kemp's Ridley reaches sexual maturity (the age when females begin to lay eggs). Green sea turtles reach sexual maturity between between 10 and 59 years of age.
  • Olive Ridleys are the most abundant of all sea turtles. Olive Ridleys have small heads and small, olive gray shells that measure around two feet in length. The average size of an adult green turtles grow is 3-4 ft. long. The average weight of mature adults is 150–419 lbs.
  • Flatback sea turtles have a flat shell, green sea turtle do not.
  • Loggerheads have the biggest heads and are known for eating crustaceans. The green sea turtle is omnivorous and eats mostly aquatic vegetation and algae.

Competition is is an interaction between organisms or species in which both the organisms or species are harmed. Limited supply of at least one resource (such as food, water, and territory) used by both can be a factor.

Green sea turtles don't have to fight with sea turtles or other sea creatures over resources.

Overproduction is a driving force in natural selection, as it can lead to adaptation and variations in a species. Darwin argued that all species overproduce, since they have more offspring than can realistically reach reproductive age, based on the resources available.

Like other turtles, green sea turtles lay eggs. Females come ashore sandy beaches to nest a few weeks after mating. Then using her hind flippers, she digs an egg cavity. A female deposits 50 to 200 Ping Pong ball shaped-eggs into the egg cavity. The eggs are soft-shelled, and are papery in texture. They do not break when they fall into the egg cavity because the eggs are surrounded by a thick, clear mucus. The female covers the nest with sand using her hind flippers. Burying the eggs serves three purposes: it helps protect the eggs from surface predators; it helps keep the shells soft and moist, thus protecting them from drying out; and it helps the eggs maintain proper temperature. After burying the eggs, the female returns back to the ocean leaving the hatchlings to fend for themselves.

After about 50-70 days, the eggs hatch and try to make it to the ocean. A remarkable percentage of hatchlings don't make it to the ocean because they are preyed upon by gulls and crabs. It is estimated that only 1% makes it to the ocean. The biggest challenge of a green sea turtle's life is making to the ocean. After making it to the ocean, green sea turtles, usually don't experience too many issues.

Other Important Facts

  • Human activities have placed nearly all species of sea turtle are classified as Endangered.
  • Killed for their eggs, meat, skin and shells, sea turtles suffer from poaching and over-exploitation.
  • They also face habitat destruction and accidental capture in fishing gear.
  • Climate change has an impact on turtle nesting sites. It alters sand temperatures, which then affects the sex of hatchlings.

Works Cited

  • http://www.savetheseaturtle.org/The-Evolution-of-Sea-Turtles.html
  • https://conserveturtles.org/information-sea-turtles-threats-sea-turtles/
  • https://seaworld.org/en/animal-info/animal-infobooks/sea-turtles/adaptations
  • http://world-turtle-trust.org/turtleinfo.html#watching
  • https://en.wikipedia.org/wiki/Green_sea_turtle
Created By
Tina McPhail
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