Divergent evolution occurs when two populations of the same species are separated and become genetically different. Two types of divergent evolution are demonstrated in Figure 2. One type is called Allopatric speciation; this occurs when a population or group of organisms belonging to the same species, are separated geographically. Over time, the separated groups develop different traits due to environmental differences. In Figure 2a, the grey fish evolved in a lake the receives salt water runoff, they would need to have evolved traits to survive the increased salinity.
Sympatric speciation occurs in the populations are not separated (Figure 2b). For some reason the two populations don’t mix even though they are in the same environment. Differences in behavior can lead to sympatric speciation. For instance, one population feeds on plants at the bottom of the lake , while the other feeds on insects near the surface. Over thousands of years of separation based on behaviors, they become different species because each population would have traits to make them better suited to eating plants at the bottom of a lake, or eating insects near the surface.
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Allopatric speciation happens when a population of a species is separated by a geographic barrier. B. Sympatric speciation happens when a population is separated by behavior.
Coevolution
Coevolution happens when two species evolve together because of the relationship they have with each other. For example, as prey gets faster to avoid being eaten, predators also have to be faster in order to eat. Coevolution can also happen between organisms with a relationship a mutualistic relationship as shown Figure 3. Pollinators, such as hummingbirds, have evolved beaks to feed on specific plants. The plants benefit because they are pollinated. Figure 3: Hummingbirds have evolved beaks that fit the flowers which they
Different characteristics of species allows for the types of niches that can be occupied and whether or not they can be coexisted for example a food specialist will have anatomical and physiological adaptations that allow it to acquire and extract energy and nutrients from one food source extremely well, but will be at a disadvantage if that food source runs low. A food generalist may not acquire as much energy from the specialist’s preferred food, but will be able to make up for that by consuming other kinds of food. We can easily envision circumstances in which either species might outcompete the other. To achieve coexistence of species the carrying capacities of certain species must not be overshot and remain
“The main lesson of biogeography is that only evolution can explain the diversity of life on continents and islands.” (Coyne 109).In convergent evolution 3 of the six components discussed in chapter 1 are working together. These 3 components are common ancestry, speciation, and natural selection. If evolution did exist, ancestors of species today that lived in the same place, when dug up, should be fossils that resemble organisms today.
a)} How may Variation Arise in Natural populations b) Explain how natural selction may bring about changes in a population and what conditions may be necessary to bri about speciation A species is a group of organisms that look alike and can reproduce successfully to produce fertile offspring. Within a species there is variation which can be caused my meiosis, random fertilisation, mutations and the natural environment. Genetic variation increases the chance for survival of a population if the environment changes. For example the introduction of a new virus in to the new environment may kill some organisms but others may be resistant to it and survive.
2. Allopatric speciation occurs due to a geographic isolation process such as when a pond might dry up and create two ponds, a flood, a river is re-routed, or a bird carries seeds in its feathers and drops the seeds in new location during the birds migration. The species of the previous geographic location also become reproductively isolated. The population then becomes two separate populations and begins to change over time due to changes in the gene pool, environments, natural selection and mutations. With this understanding it is possible to see that plate tectonics theory and continental drift theory possibly resulted in allopatric speciation.
Define evolution? A slow change of something into better form. The word evolution means change, and the process of evolution reflects this definition as it applies to populations of organisms. Biological populations are groups of individuals of the same species that are sub-divided from other populations by geography and are somewhat independent of other groups. Biological evolution, then, is a change in the characteristics of a biological population that occurs over the course of generations. The changes in populations that are considered evolutionary are those that are inherited via genes. Changes that may take place in populations due only to short-term changes in their environment are not
Natural selection is one of the main methods in which speciation occurs through the following steps: • Within a population of one species there is genetic diversity, which is called variation. • Due to the natural variation some individuals will be fitter than others. • Fitter individuals
comes from and how they evolved in the manner that they did. This type of
Commensalism is when one species can benefit from a relationship and not hurt the other. There are four different main types; chemical, inquilinism, metabiosis and phoresy. Chemical commensalism is most often observed between bacteria. It involves the species of one bacteria feeding on the chemicals produced or the waste products of the other bacteria. Inquilinism involves one species using the body of another organism as a platform or living space while the host does not benefit or is harmed. Metabiosis occurs when one species unintentionally creates a home for another species through one of its normal life activities. A phoresy takes place when one organism attaches to another organism specifically for the purpose of gaining transportation. An example of commensalism (inquilinism) is barnacles and whales. Barnacles are non-moving and they rely on currents to bring them food. Some barnacles attach themselves to whales in order to help them live. They can benefit as they are then transported over the ocean which exposes them to more feeding oppurtunities. The whale neither benefits or is harmed by the barnacles.
2; Echelle 2008). The three species diverged from one another in the last one million years, with C. diabolis falling out most recently some 0.5 MYA. The speciation is believed to be allopatric, but there is still some uncertainty regarding C. diabolis (Duvernell & Turner 1998). The reason for this uncertainty is that the cavern that C. diabolis currently inhabits, Devil’s Hole, only opened to the surface around 60,000 years ago (Martin et al. 2016). It is possible that there was some degree of sympatric speciation happening before a colonization event occurred or, because mtDNA was used to determine divergence times, C. nevadensis could have been polymorphic for mtDNA before the cavern opened and was subsequently colonized (Echelle 2008). So how did the allopatric speciation of the Death Valley pupfish occur? Was it the result of dispersal or vicariance?
Evolution is a change in genes of a population over time. Speciation is a process of gene changes which cause one population to become 2 unique populations. Speciation can be illustrated using the lemurs of Madagascar as an example. The evolutionary and biogeographic processes experienced by the lemurs are not unusual.
Perhaps, where they coexisted, some difference prevented interbreeding or the production of hybrids between these populations and early human ancestors. Usually such differences between related species originate as adaptations to the environment, not as devices for reproductive isolation.
There is another side to the biodiversity of the evolutionary field, as the population weakens the species start the inbreeding of smaller populations, thus playing a role in the extinction of a species. Inbreeding is reproduction among members of a species that are genetically similar. The genetic inbreeding is designed to bolster populations of species whose numbers are in decline. However, when only a few species or varieties of a species are cultivated or survive, the genetic diversity of the organism declines, and population is more vulnerable to being wiped out by new diseases or climate changes because of the inbreeding (Alters, 2000).
Other essential factors include, steadiness of numbers and overpopulation, which led to battle for survival amongst the species and only some will live sufficiently long enough to breed. Additionally, variation amongst the offspring plays a role in survival as well where only the strongest will survive through extreme conditions. Also, the arrangement of new species where members lacks favourable capabilities and characteristics are most likely not to survive sufficiently long to breed. Inheritance of a single variation will not create another species. However, the evolution of various varieties in a specific course over the generations will lead to the evolution of other type
Vicariance is define is a branch of biogeography that occurs when a population of species are separate by a physical barrier as the result of a geological event. In principle, vicariance can also be defined as division of the land and species on it. Vicariance events (like mountain passes and river formation) often caused physical barriers that block gene flow between a population of species. If a population of species was separated by vicariance event, the limited gene flow and selective pressures occurring would result and the species becoming more genetically different. This would eventually cause the population to be establish as separated sister species. For speciation to be the result of vicariance, the timing of the vicariance event
Evolution refers to change over time as species modifies and separate to produce several offspring species.