Biology: Biology: Speciation

Speciation

Deforestation is a example of Adaptive Radiation

Building dams over habitats are a immediate impact
on organisms

Evolution is a process that is accepted all around Biology. But how do we actually get our new species? Well first we must know what a species is. A species is a group of populations whose members produce a fertile offspring. A species does not just magically appear from out of no where, it is created from another species. Speciation is when one species to two species. Eventually, if the species does not survive the species will die off. Extinction is when one species turns into no species. Speciation rates can vary from being very fast in a couple of generations in a species to being very slow taking millions of years for a new species to develop. Adaptive radiation is a process where a species is introduced to a new habitat. Adaptive radiation can occur instantly. A example of adaptive radiation is a volcanic eruption. The process usually occurs very fast and its effects can be felt immediately in the organisms. Plants and animals are killed and separated. Another example is the impact of humans. As the human population has risen during the years so has the extinction rate especially in recent years where our population has jumped.

There are two types of adaptive radiation, allopatric speciation and sympatric speciation. Allopatric Speciation is when a population is divided which leads to speciation. This is usually with a geographic barrier such as a mountain or river. Eventually the speciation will occur. The other type of speciation is sympatric speciation where a population is not divided by anything at all. A process that occurs in plants but not in animals is Poyploidy. Polyploidy is when the plant is given a extra pair of chromosomes during cell division. Autopolyploid is when two sets of chromosomes from a single species of plants. Allopolyploid are sterile hybrids changed to fertile polyploids by mutation. Macroevelution is the end result of many many speciations through time. Heterochrony is a change in the rate or timing of a developmental event. A organisms shape largely depends on the growth of development. Babies have a much faster developmental rate than a maturing teenager. Paedoorphosis species retains as an adult juvenile features of an ancestor. Genes largely effect what and how much you develop. Homeotic genes are genes that tell you how much of your body will grow. For example, babies homeotic genes tell how tall you will be or how large your brain will be. The Hox gene is a type of homeotic genes that can have a massive impact on morphology.

Reproductive Isolation?

Trust me this section will make complete sense at the end. Reproductive isolation are barriers that impede members of two different species from producing a fertile offspring. A.K.A no gene flow from each other. Reproductive Isolation is broken up into two sections, pre - zygotic barriers and post zygotic barriers. These barriers impede before or after fertilization.

Pre-zygotic Barrier

Pre zygotic barriers are barriers that impede mating or hinder fertilization. Habitat isolation is when the two species rarly encounter each other like one species of dog lives in Spain and a other species of dog lives in China. Temporal isolation (temperature isolation) is when two species breed at different times such as a species breeds during the day while another breeds in the night.. Mechanical isolation is differences between fertilization basically meaning its physically impossible for them to mate due to a different structure for fertilization. Gametic isolation is when the sperm and the egg are not compatible.

Post-zygotic barriers

Post-zygotic barriers are barriers that prevent the hybrid zygote from becoming a fertile adult. There are three barriers that are apart of Post-zygotic barrier. Reduced hybrid viability are genes of different species that impair the hybrid. Reduced hybrid fertility are sterile hybrids that are created due to uneven chromosome numbers. A example of this is a mixture between a horse and a donkey, even though they produce a mule, a mule cannot reproduce. The finally part is hybrid breakdown which is when the hybrid is fertile but the next generation is sterile.

Morphological species concept are characterized species by shape, size, and others. subgeneric gene flow. Another is the paleontological species concept which is morphologically distinct species from fossil record. phylogenetic species concept is a species as a set of organisms with a unique genetic history.