Chapter 17
Sexual Reproduction
Gene Pool #
Phyletic speciation
Divergent Speciation #
Biological Reproductive Barriers
Gene pools are important due to the fact that genetic diversity can give the best traits to all of a species.
The gene pool in humans is easy to see - people have red hair, blonde, brunette, dark skin, light skin, etc.
A gene pool is a collection of genotypes with a large amount of diversity.
Without sexual reproduction, a gene pool would be almost non-existent.
Sexual reproduction results in a 50% share of genes between the two parents, resulting in offspring that will carry possible desirable traits.
Sexual reproduction creates gene pools through gene sharing.
Conditions required for natural selection to occur
Reproduction
Heredity #
Without heredity, good traits could not be passed down to the offspring.
Heredity is a very important process in creating an organism that can adapt and overcome.
Heredity is the cause of desirable traits being passed on.
When organisms are reproducing, genes are shared and traded from parents to offspring.
For example, if your past generations of family had a history of heart disease, you would be at risk for the susceptible genes being part of your makeup.
Reproduction is the gateway for genes to be sorted and passed on to the next generation.
While population split ups are common, it is more rare for a population to become so differentiated from the original group to be considered another species.
While the different species may appear similar, the species have evolved differently - even though it may be hard to see.
Phyletic speciation is the result of one population diverging from the original group.
This form goes as follows; Species 1 evolves into species 2 further down the line, which evolves into species 3..
Phyletic speciation occurs as long as the species continues to follow changes in the environment.
Phyletic speciation is a much more linear form of evolution that Divergent speciation.
Convergent evolution
For example, many sharks are different species, but many if not all carnivorous sharks have sharp teeth with which to kill prey.
Convergent evolution occurs when organisms in the same environment share similar traits.
Breeding barriers can cause a species to split into two separate reproductive groups.
For example, if a mountain range split up a population of goats, the goats would evolve differently on either side of the mountain if the conditions were different.
Gene pools are a little like drawing straws - some traits are better than others, but the diversity is good for reproduction.
Incest is the result of a complete lack of a gene pool, and this typically results in deformation or disability.
Sexual reproduction mixes genes back and forth.
Some bacteria that do not take part in sexual reproduction essentially are the same as they always have been.
This is due to the fact they have no genes to pass on but their own.
This is why bacteria that are asexual have the same genetic code over and over.
Sexual reproduction requires a gene pool, though, as many examples of incest and their consequences are available from the interbreeding of royal families across the globe.
Over time, this could lead to the development of a new species.
Phyletic separation is essentially an organism evolving so much, that it cannot be considered the same organism it was.
Although the species originated from the original grandfather, it is too different ot be the same species. An example of this is Homo Sapiens and Homo Erectus.
If an animal survives more readily than another of the same species hereditary will ensure this desirable trait is passed on to the next offspring.
An example of this is a moth of a white color survives in a snowy environment more than a brown moth - this trait will become common.
If not for heredity my beautiful eyes would be lost to the mixing bucket of reproduction.
Although that was conceited, heredity gives some order to sexual reproduction.
If not for heredity sexual reproduction would only result in constant mixing of genes, with no sense of direction.
An example of this is the wooly mammoth and common elephant.
While this is an easy to spot comparison some examples aren't so focal.
Reproduction is the spinning of the bingo balls.
Some desirable traits are passed and some not-so desirable traits may be passed.
Hence, the mixing - it is somewhat a gamble.
Two different environments could call for two different sets of traits in order to survive.
The winning trait will survive more readily and thus become the dominant trait.
Another good benefit of sexual reproduction is that not all eggs are put into one basket, so to speak.
If all humans had a susceptibility to the common flu that led to a 100% mortality rate, extinction would be inevitable.
An example of a lack of diversity being bad was the Irish potato famine.
Thankfully sexual reproduction wouldn't allow this - while some would be vulnerable, others would not be vulnerable, and survive.
Nearly all of the potato plants, being vulnerable to blight, were devastated by the disease.
A more diverse gene pool could have helped prevent this. #
