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Evolution
The scientific theory according to which populations change gradually through a process of natural selection.
5,264 Questions
Which family of organic molecules is a hydrocarbon?
Alkanes are a family of organic molecules that consist entirely of carbon and hydrogen atoms with single covalent bonds. They are a type of hydrocarbon due to their composition of only carbon and hydrogen atoms.
Explain what is meant by the term evolution?
The term itself refers to the gradual shift of something over time.
More specifically, in biology it refers to the gradual shift in traits in a population as caused by natural selection. Traits which are harmful or cause an organism to have a decreased chance to survive are 'selected against' in that they are less likely to pass on those traits. Likewise, traits which are beneficial cause there to be an increased chance the organism will survive to pass on it's traits.
Two theories on how species change over time?
- The theory of natural selection proposed by Charles Darwin suggests that species evolve over time through the process of differential survival and reproduction of individuals with advantageous traits.
- The theory of genetic mutation and genetic drift posits that changes in the genetic makeup of a population occur due to random mutations and genetic variations over generations, leading to new traits and species.
When genetics refer to the physical characteristics of an organism they are talking about its what?
Phenotype. The physical expressed characteristics of an organisms genotype is known as its phenotype. Two organisms may have the same phenotype, but different genotype depending on the dominate or recessive genes present. Just remember physical=pheno.
Why do members of chromosome pairs separate during mitosis?
Members of chromosome pairs separate during mitosis to ensure that each daughter cell receives the correct number of chromosomes. This separation is necessary to maintain the correct genomic content in offspring cells and prevent abnormalities such as aneuploidy.
The mechanism of evolution by natural selection was presented by Darwin and?
it states that individuals with advantageous traits are more likely to survive and reproduce, passing those traits on to future generations. Over time, this process leads to the accumulation of beneficial traits in a population, driving the evolution of species.
The greatest biodiversity on earth is found in the?
In general, biodiversity globally is high in the Tropical World
of the humid tropics and the extremely infertile Unenriched World
of the ancient arid landmasses of Australia and Southern Africa. Biodiversity is much lower in the geologically young and cool Enriched World
which basically corresponds to the extratropical northern and western hemispheres, plus New Zealand (which can very easily be thought of as part of the western hemisphere though it is on the other side of the International Date Line).
Although it is popularly though that high biodiversity relates to the more “benign” and less demanding environment in hot climates, recent research by Michael Huston of the University of Texas in “Biological diversity, soils, and economics” and “Precipitation, soils, NPP, and biodiversity: resurrection of Albrecht's curve”, Australian ecologist Tim Flannery in The Future Eaters
plus Jason Weir and Dolph Schluter in “The latitudinal gradient in recent speciation and extinction rates of birds and mammals” show that these are misconceptions.
Flannery and Huston both demonstrate that owing to the roughly four orders of magnitude greater age of their soils (except in the volcanic regions of the Pacific Rim), the productivity of the Tropical and Unenriched Worlds is very much less than those of the Enriched World of the extratropical northern and western hemispheres. Weir and Schluter show that speciation rates are much lower in the Tropical World than in the depauperate fauna of the Enriched. One would presume that with their extreme geological stability the Unenriched World of Australia and Southern Africa would have still lower speciation rates than the humid tropics
. This is especially true when one considers that many birds and mammals in Australia and Southern Africa require so much labour for reproduction that most adults must serve as “helpers at the nest” rather than reproduce on their own, which acts as an extremely severe limiter on potential dispersal.
All these indicators point to the higher diversity of the Tropical and Unenriched Worlds as being due to reduced interspecific competition
compared to the young and highly productive Enriched World. Soils of an infertility universal in all of the Unenriched and most of the Tropical World are exceedingly rare in the Enriched World - occurring only in a few areas of exceptionally nutrient-poor parent materials
like ultrabasic rocks (serpentines, peridotites) - and then only outside of glaciation limits within which intrazonal parent materials are converted to highly fertile zonal soils. (In this context, it’s notable that the most northerly major biodiversity hotspot in the Klamath Basin is one of the major occurrences of serpentines in the world, as is the very rich tropical hotspot of New Caledonia).
In the Tropical and Unenriched World resources are so scarce in unfertilised environments that co-operation rather than competition tends to be the rule to allow plants to obtain the minimal nutrition possible on these soils. The absence of competition reduces extinction rates to a fraction of the level observed throughout the Enriched World: in essence, the creation of biodiversity occurs in the Enriched World, but it is rapidly pooled into reservoirs in the Tropical World, and the Unenriched retains older species (marsupials, mousebirds) dating from periods when its ecological conditions were globally general.
How do evolutionists believe coal formed?
Evolutionists believe coal formed over millions of years from the remains of ancient plants that were buried, compressed, and heated under the Earth's surface. The process of coal formation is part of the carbon cycle and involves the transformation of organic matter into a carbon-rich substance due to geological processes.
Can zombies survive in Alaska?
If a zombie could exist, the brain would have to remain alive in order to send neurological impulses to the musculature in order to ambulate. Brain and musculature both would be the only systems still getting oxygen, delivered by the animating Z-factor, probably by osmosis, but nowhere near as efficiently as a functional cardiopulmonary system.
A human body, even a dead one, is still about 90% water, and water freezes in the winter when the temperatures drop below 32 degrees Fahrenheit. Zombies have no body heat, so they would freeze solid, including moisture in their brain. When water freezes, it expands, so any fluid in the brain or around it such as the subarachnoid area on the surface of the brain would freeze and cause rupturing of the brain tissue and extensive trauma, destroying the zombie in all likelihood.
Even if they could somehow survive such brain trauma, they would be frozen solid, unable to move, and would be easy pickings for any human with a weapon.
If a zombie could exist, the brain would have to remain alive in order to send neurological impulses to the musculature in order to ambulate. Brain and musculature both would be the only systems still getting oxygen, delivered by the animating Z-factor, probably by osmosis, but nowhere near as efficiently as a functional cardiopulmonary system.
A human body, even a dead one, is still about 90% water, and water freezes in the winter when the temperatures drop below 32 degrees Fahrenheit. Zombies have no body heat, so they would freeze solid, including moisture in their brain. When water freezes, it expands, so any fluid in the brain or around it such as the subarachnoid area on the surface of the brain would freeze and cause rupturing of the brain tissue and extensive trauma, destroying the zombie in all likelihood.
Even if they could somehow survive such brain trauma, they would be frozen solid, unable to move, and would be easy pickings for any human with a weapon.
Edit: as much as I like answers from my Contacts, I need to clarify a point about clothing. Clothing is not inherently "warm" - it is inherently "insulate. A jacket cannot "warm you up" if you have no body heat for the jacket to trap and conduct back to you. Clothing also reduces skin-to-air loss of heat by minimizing conduction and convection of air currents over your skin, but that doesn't help if you have no body heat in the first place. No offense, I just had to clarify that point
What are the theories of Lamarck and Darwin on why cave fish loose their eyes?
Lamarckian evolution is based on the notion that changes that happen to an organisms physiology are passed on when it reproduces. Taking this to an extreme to show why it has been discredited, a person who loses their arm during their childhood does not have babies that are born with one arm. With regard to cave fish, Lamarcks theory of evolution argues that they lose their eyes during their life, and pass on this "lack of eye-ness" to their offspring. Modern genetics has further dampened this idea, as acquired characteristics are not carried in genes.
Darwinian evolution argues that, at some point during the cave fishes history, a genetic mutation caused one to be born with no eyes (or more likely, one was born with slightly less functional eyes). These fish, due to the nature of their dark environment, would be at no disadvantage to their fully sighted brethren. Eyes can easily get infected or irritated, so nature may have favoured on the side of the eyeless ones. Over time blind cave fish became dominant, eventually reaching the pinnacle of existence by being discussed on the internet.
Hope that helps.
Which mollusk is predatory and does not have an outer shell?
Both predator and prey as with most animals in this world.
What are Darwin's four postulates?
1. There is variation in individuals within a species
2. Variation ensures that individuals that are better suited to their environment will survive.
3. Traits that assist individuals in survival and allow them to reprduce gradually spread throughout population.
4. Individuals produce more offspring than the local resources can support.
Required for a new species to form?
For a new species to form, there needs to be a separation in gene flow (such as physical isolation or reproductive barriers) between populations, allowing for genetic divergence over time. This can lead to the accumulation of unique genetic and phenotypic traits that eventually define the new species. Additionally, natural selection plays a crucial role in driving the adaptation and survival of the new species in its specific environment.
Convergent evolution is the pattern of evolution where two unrelated species develop similar traits due to similar environmental pressures. This can lead to analogous structures in different species that serve the same function, even though they do not share a common evolutionary origin.
Evolution is not inherently misleading; it is a fundamental concept in biology supported by extensive evidence. Misunderstandings or misconceptions about evolution may arise from incomplete or incorrect information, personal beliefs, or deliberate misinformation. It is important to rely on scientific evidence and critical thinking to understand the complexities of evolution accurately.
Is the fossil record valid evidence for evolution?
Yes, the fossil record is considered a valid and significant piece of evidence for evolution. Fossils provide a record of past life forms and show a progression of species over time, supporting the idea that organisms have changed and diversified through evolutionary processes. Additionally, the discovery of transitional fossils helps to fill in gaps and provide connections between different groups of organisms.
When did the first cells appear on earth?
The first cells appeared on Earth approximately 3.5 billion years ago during the Archean Eon. These cells are believed to be simple, single-celled prokaryotes.
The theropods were bipedal because they were carnivrous hunters. Running on two feet allowed them to be swift and agile so they could hunt prey better. This rendered their forelimbs unimportant so they grew small.
Why is there a gap in hominids between 3 mill BCE and 2 mill BCE?
From the fossil record, AustraIopithecus afarensis is now known to have lived between 4 and 2.5 million years ago.
Australopithecus africanus lived between 3 and 1 million years ago.
Australopithecus robustus is now known to have lived between 2.5 and 1.5 million years ago.
Australopithecus boisei lived between 2.5 and 1 million years ago.
Homo habilis also lived between 2.5 and 1.5 million years ago.
No doubt, further discoveries will continue to fill out this picture, but there is already a wealth of information about the early hominids who lived between 3 and 2 million years ago.
How much DNA do humans have in common with a tree?
Humans and trees have approximately 25% of their DNA in common due to shared genes inherited from a common ancestor. The differences in DNA sequences account for the diverse traits and characteristics that distinguish humans from trees.
Does homologous mean that structures are similar due to having common ancestry?
homologous structures- same structure/different functions in common ancestors
analogous structures-same functions/differnt structures not in common ancestors
vestigial-show evolutionary history/structures that arent used anymore (i.e. human appendix/human tailbone)
What makes the protists group unique or different?
Protists are a diverse group of eukaryotic organisms that do not fit into other kingdoms like plants, animals, or fungi. They can be unicellular or multicellular and exhibit a wide range of forms and lifestyles. Protists play various ecological roles, from being photoautotrophs to predators, parasites, and saprobes.
Phylogenetic hypotheses are strongest when?
Phylogenetic hypotheses are strongest when they are supported by multiple lines of evidence, such as morphology, genetics, and fossil data. Additionally, hypotheses that are consistent with principles of evolutionary theory and show high levels of statistical support are considered strong.
Describe margulis' theory about the evolution of protists?
Lynn Margulis proposed the endosymbiotic theory, suggesting that eukaryotic cells originated from the incorporation of prokaryotic cells through symbiosis. She specifically highlighted the role of bacterial ancestors, such as mitochondria and chloroplasts, in the evolution of protists. According to Margulis, these symbiotic relationships contributed to the complexity and diversification of protists.
