Goal 3 - Evolution Theories Notes
REMEMBER EVOLUTION = CHANGE IN A POPUALTION OVER TIME!
Jean-Baptiste Lamarck
Jean-Baptiste Lamarck
- 1806 – Evolutionary theory based on principle of use and disuse and the inheritance of acquired characteristics.
- Principle of use and disuse – new structures appeared in the course of evolution because they were needed.
- Structures that were present and were used became better developed and increased in size (ORGANISMS IMPROVED); structures that were not needed or not used much decreased in size, and eventually disappeared (DON’T USE IT YOU LOOSE IT).
- Inheritance of acquired characteristics – evolutionary changes occurred when traits acquired during the lifetime of an individual were passed on to offspring (AQUIRED TRAITS).
- Examples giraffes – though ancestors had short necks, stretched to reach top leaves, and passed on the trait.
- DUMB = because we know individuals can’t develop a trait unless their genes code for it to do so!
Charles Darwin
Charles Darwin
In 1831, Charles Darwin went on a voyage on the HMS Beagle to South America and the South Pacific. He was the ship’s naturalist meaning he studied and collected organism’s including fossils wherever the ship stopped.
Darwin knew that many species produce large numbers of offspring yet they did not over run the Earth. He realized that individuals must struggle to survive. Types of struggles include: competition for food, space, escaping predators, finding mates, and locating shelter.
Natural Selection is a mechanism for change in populations when organisms with certain variations survive, reproduce and pass on their variations to the next generation. Organisms without these variations are less likely to survive. Variations in a population provide material for natural selection to work!
In 1831, Charles Darwin went on a voyage on the HMS Beagle to South America and the South Pacific. He was the ship’s naturalist meaning he studied and collected organism’s including fossils wherever the ship stopped.
- Darwin was particularly fascinated by the Galapagos Islands located in South America. He saw that the species of plants and animals were unique to the island that they came from but were very similar to the species elsewhere.
- This made Darwin think that species change over time.
Darwin knew that many species produce large numbers of offspring yet they did not over run the Earth. He realized that individuals must struggle to survive. Types of struggles include: competition for food, space, escaping predators, finding mates, and locating shelter.
- All of this led to Darwin’s final theory of Natural Selection. He published his book called “On the Origin of Species” in 1859. At the same time a man named Alfred Russell Wallace in Indonesia developed the same idea.
Natural Selection is a mechanism for change in populations when organisms with certain variations survive, reproduce and pass on their variations to the next generation. Organisms without these variations are less likely to survive. Variations in a population provide material for natural selection to work!
Natural Selection
Darwin – Theory based on the presence of variations among members of a species and the process he called natural selection. His theory includes the following ideas:
Overpopulation – within a population, there are more offspring produced in each generation that can possibly survive.
Competition – the natural resources (food, water, and space) available to a population are limited. Because there are more organisms produces in each generation than can survive there must be competition between them for the resources needed for survival.
Survival of the Fittest – Variations among member of a population make some of them better adapted to the environment than other. Generally the best-adapted individual survives.
Natural Selection- The environment is the agent of natural selection, determining which adaptations or variations are helpful and which are harmful. For example, if an environment is undergoing a period an unusual cold period, animals born with fur that is thicker than normal will survive more easily than animals with thinner fur. In this case variation – thicker fur- is helpful in terms of environmental pressure.
Reproduction – individuals with helpful variations tend to survive and reproduce, transmitting these variations to their offspring.
Speciation – The development of a new species, or speciation, occurs as variations or adaptations accumulate in the population over many generations.
In Darwin’s theory, environmental pressures act as a force for the natural selection of the best-adapted individuals – those with helpful adaptations enable them to survive and reproduce successfully.
Darwin’s theory did not explain how variations arise in members of a species.
Overpopulation – within a population, there are more offspring produced in each generation that can possibly survive.
Competition – the natural resources (food, water, and space) available to a population are limited. Because there are more organisms produces in each generation than can survive there must be competition between them for the resources needed for survival.
Survival of the Fittest – Variations among member of a population make some of them better adapted to the environment than other. Generally the best-adapted individual survives.
Natural Selection- The environment is the agent of natural selection, determining which adaptations or variations are helpful and which are harmful. For example, if an environment is undergoing a period an unusual cold period, animals born with fur that is thicker than normal will survive more easily than animals with thinner fur. In this case variation – thicker fur- is helpful in terms of environmental pressure.
Reproduction – individuals with helpful variations tend to survive and reproduce, transmitting these variations to their offspring.
Speciation – The development of a new species, or speciation, occurs as variations or adaptations accumulate in the population over many generations.
In Darwin’s theory, environmental pressures act as a force for the natural selection of the best-adapted individuals – those with helpful adaptations enable them to survive and reproduce successfully.
Darwin’s theory did not explain how variations arise in members of a species.