Evolution

Punctuated equilibrium is a theory in evolutionary biology that suggests long periods of stability in species are interrupted by rapid periods of change due to significant environmental shifts. During these rapid changes, new species may arise relatively quickly compared to the overall stability of the species. This theory contrasts with the gradual change proposed by traditional evolutionary theories like Darwin's theory of natural selection.

Isolation of populations, wherein two groups of the same species become separated geographically or reproductively, can lead to speciation as each group evolves independently over time. Additionally, genetic mutations and natural selection pressure can contribute to the divergence of traits between the two groups, eventually leading to the development of new species.

Evolution produces new species through a process called speciation, where populations of a species become reproductively isolated from one another, leading to the accumulation of genetic differences over time. This can occur through mechanisms such as geographic isolation, genetic mutations, and natural selection, ultimately resulting in the emergence of distinct species that can no longer interbreed.

Two factors that lead to the evolution of species are genetic variation, which introduces differences among individuals in a population, and natural selection, which favors certain traits that improve the chances of survival and reproduction in a specific environment. Over time, these two factors can result in the accumulation of adaptations that lead to changes in the characteristics of a species.

Evidence such as fossils, comparative anatomy, and DNA sequencing allows scientists to trace relationships between past and present life forms. By studying similarities and differences, they can reconstruct evolutionary lineages and understand how different species are related to each other through common ancestry. This helps us piece together the evolutionary history of life on Earth and how species have changed and adapted over time.

The four principles of natural selection (variation, inheritance, differential reproduction, and adaptation) are necessary for natural selection to occur because they describe the process by which certain traits are passed on to future generations based on their ability to help individuals survive and reproduce in their environment. Variation provides the raw material for natural selection, inheritance ensures that beneficial traits can be passed down, differential reproduction leads to the accumulation of advantageous traits in a population, and adaptation allows organisms to better survive and thrive in their environment over time.

The theory of evolution holds the belief that advanced species arose from simpler life forms through the processes of natural selection and genetic mutation over long periods of time. This theory was proposed by Charles Darwin in the 19th century and is supported by a large body of evidence from various scientific disciplines.

The fossil record and observations of extant organisms support both punctuated equilibrium and gradualism. Transitional fossil forms represent periods of gradual change, while sudden appearances of new species or rapid changes in morphology can indicate episodes of punctuated equilibrium. Both patterns are consistent with the theory of evolution, each reflecting different modes of evolutionary change over time.

A survival gene is a gene that increases an organism's ability to survive and reproduce in its environment, leading to its higher prevalence in the population over time through natural selection. These genes are advantageous for the organism's survival and reproduction, ultimately contributing to its evolutionary success.

Fitness in Darwinian evolution refers to an organism's ability to survive and reproduce in a given environment. Organisms with traits that enhance their ability to survive and produce offspring are considered more fit, leading to a higher likelihood of passing on their genes to future generations. Thus, fitness is a key factor in natural selection, shaping the characteristics of populations over time.

Bacteria would evolve faster than humans due to their shorter generation times and larger population sizes, allowing for quicker adaptation to environmental changes and mutations to occur. Humans have longer generation times and smaller population sizes, slowing down the rate of evolution.

Biochemical similarities among different species, such as shared genetic sequences and metabolic pathways, provide evidence for a common ancestry and evolutionary relationships. These similarities suggest that organisms have evolved from a common ancestor and have undergone genetic changes over time. Studying biochemical similarities helps scientists understand the processes of evolution and how species have diversified and adapted to their environments.

through reproductive isolation........ wba secure?

In sexual reproduction an entirely new individual is produced. The genes are not exactly the same as either parent. In asexual reproduction the new individual is exactly the same as the parent. It is a cone of the parent.

Embryonic development can be used as evidence for evolution because it shows similarities in the early stages of development across different species, known as embryonic homologies. These similarities suggest a common ancestry and evolutionary relationships between organisms. By studying how embryos of different species develop, scientists can gain insights into their evolutionary history.

Bear with me in the first few lines. We need to 'conclude' (hypothesise) that evolution exists at all before I show you the evidence.

All life is so very similar. If you start with an elephant and a wildebeest, you will notice that both have backbones, red blood cells without a nucleus, more than one type of tooth, are warm-blooded and give birth to live young. Where does such similarity come from unless these two species have a common ancestor? They have inherited their similarities from a common ancestor. That is the main conclusion so far. We have begun our delve into evolutionary theory.

If you go back far enough you will notice the similarities in DNA between ALL organisms. Thus Escherichia coli and wildebeest and pelicans and palm trees all have a common ancestor. How else could they be so similar? It is an inevitable conclusion that a set of living organisms (two or three or all) must have common ancestry due to their similarity. That is the first step in supposing evolution to be true.

Obviously to go from a common ancestor (in the past) now requires change (to go to the future) to get from a common ancestor of a wildebeest and an elephant to the extant wildebeest and elephant. Or indeed from the common ancestor of all life to today's elephant and pelican and palm tree and polychaete and so on. Right, so now to the main answer. Where is the evidence of evolution (change) that the questioner seeks?

On the biggest scale, the fossils in rocks show a specific sequence of life from the Precambrian origin of life until now. Fish are the earliest fossil vertebrates, followed a bit later by ancient amphibians, followed by ancient reptiles, followed by ancient mammals right up until today's explosion of beautiful life. The sequence is important. The earliest amphibians (ichthyostegalians) must have evolved from ancient sarcopterygian fish, similar perhaps to today's coelacanth or lungfish. The earliest mammals evolved from a branch of reptiles and did not precede them nor appear concurrently with the earliest of reptiles. It was a branch of mammal-like reptiles that gave rise to the mammals. The fossil sequence in other words supports our 'model' of evolution across Earth's history.

And the fossil record shows change in other ways. If birds evolved from a branch of dinosaurs then there should be something very much like a dinosaur that has the occasional obviously avian feature. Enter Archaeopteryx. Was it the earliest bird or a dinosaur? Can we decide? The point is that Archaeopteryx had jaws in its mouth like a dinosaur but feathers like a bird. Let's call Archaeopteryx a feathered dinosaur. And it wasn't the only one. Sinosauropteryx and many other feathered dinosaurs have been discovered, including the tyrannosaur Yutyrannus. That is what we expect in an evolutionary model. It is very unlikely that we will find one single species linking one major group to another (here, dinosaurs to birds). Life is too prolific and too speciose for that. The point is that Archaeopteryx is one illustration of change.

The platypus is another. Ancient platypuses (of the genus Ornithorhynhus? - perhaps not) illustrate the transition from reptiles to mammals. Ornithorhynchus anatinus, the extant platypus, lays eggs like a reptile but feeds its young on milk like a mammal. Platypuses will have survived 'unchanged' from the earliest days of mammalhood until today. Not true. Certainly not to my understanding. Now for the power of DNA as a driver of evolution.

Platypuses illustrate the ancient transition of reptile to mammal. But the extant platypus I doubt is 'unchanged'. During the production of gametes (of any eukaryotic organism) DNA really is shuffled. During prophase of meiosis, DNA crosses over between the chromosomes (forming chiasmata), mixing it more than it is to be mixed already. Also, one's mother-inherited genes and one's father-inherited genes are randomly segregated between the gametes that one's self makes, really giving an eclectic mixture of gene mixtures to the next generation. Thus variation perpetuates, generation after generation. With such mixing of DNA, evolution is more likely than not, because the mixing of DNA brings variation into the world.

Next for Natural Selection. This is the phenomenon whereby some variants are better at surviving from birth to adulthood than others. And that's not all. The most successful variants, after all that (escaping predators and finding food and escaping all those terrors and turmoils) leave even more offspring than their competitors. Organisms, in other words, should behave as if they 'want' to leave more offspring than their competitors. Why else would antelope be so violent over acquiring mates before their rivals? A subset of Natural Selection is called Sexual Selection. You can see where this is going. Those violent male antelope win themselves a harem, so that means the genes of a single male are passed on to many females. Sexual Selection (in the depths of animal behaviour science) illustrates very while how traits develop. You can easily imagine the growing and growing of horns for these battles. The sons of the harem leaders will have them. And the sons of the biggest harem leaders will have the best. Big-hornedness (let's call it megakeraty for fun) will outcompete small-hornedness. And so a population should change (evolve) from small-horned to big-horned.

Here we have the realms of evidence that support evolution. The fossil record, DNA and animal behaviour and anatomy. There's actually much more.

Sexual selection can affect reproductive success by influencing the ability of an individual to attract a mate and successfully reproduce. Traits that are favored in mate selection, such as physical attractiveness or elaborate courtship displays, can increase an individual's chances of mating and passing on their genes to the next generation. Additionally, competition for mates can result in certain individuals being more successful in mating and producing offspring.

Stephen Gould supported his theory of punctuated equilibrium with evidence from the fossil record, noting that species show long periods of stability followed by sudden bursts of change. He argued that this pattern is better explained by rapid speciation events rather than gradual evolution. Additionally, Gould highlighted gaps in the fossil record as evidence for his theory.

Many years of evolution are likely to produce organisms that are well adapted to their environment, showing traits that increase their chances of survival and reproduction. This process results in greater diversity and complexity, allowing species to thrive and successfully pass on their genetic traits to future generations.

population

1. Fossil record: The transition of species over time, as documented through fossils, provides indirect evidence of evolution and common ancestry.

2. Comparative anatomy: Similarities in the anatomical structures of different species, such as the pentadactyl limb in vertebrates, suggest a shared evolutionary history.

Scientists are interested in studying the rate of evolution because it provides insights into how species have changed over time. By understanding the pace at which genetic variations accumulate in populations, researchers can better comprehend the mechanisms driving evolution and its impacts on biodiversity. The rate of evolution can also inform predictions about how species might respond to environmental changes.

Charles Darwin's ideas on evolution were likely influenced by observing the variations in species during his travels, as well as by reading works on geology and the idea of gradual change over time. He proposed that natural selection, where individuals with advantageous traits are more likely to survive and reproduce, is a key mechanism driving evolution.

Many organisms became extinct in the late cretaceous and even before the K-T extinction event. Possibly one reason is that seed ferns had been losing the battle to the rising tide of agiosperms ( flowering plants ).

Numerous scientific disciplines, such as genetics, paleontology, and comparative anatomy, provide evidence supporting Darwin's theory of evolution. Fossil records show transitional forms between species, genetic studies demonstrate shared ancestry through common DNA sequences, and observations of natural selection in action support the idea of species evolving over time. These various lines of evidence collectively contribute to the scientific consensus on the validity of Darwin's theory of evolution.