Tarantulas are among the most notorious spiders, due in part to their size, vibrant colors and prevalence throughout the world. But one thing most people don't know is that tarantulas are homebodies. Females and their young rarely leave their burrows and only mature males will wander to seek out a mate. How then did such a sedentary spider come to inhabit six out of seven continents?
The first photosynthetic oxygen-producing organisms on Earth were cyanobacteria. Their evolution dramatically changed the Earth allowing oxygen to accumulate into the atmosphere for the first time and further allowing the evolution of oxygen-utilizing organisms including eukaryotes. Eukaryotes include animals, but also algae, a broad group of photosynthetic oxygen-producing organisms that now dominate photosynthesis in the modern oceans. When, however, did algae begin to occupy marine ecosystems and compete with cyanobacteria as important phototrophic organisms?
Using mathematical modeling, researchers considered a time very early in evolution when primordial species reproduced using external fertilization. In the model, bigger reproductive cells, or gametes, presented a competitive edge because they could hold more nutrients for a potential zygote. Smaller gametes, however, required fewer resources to make, which put less stress on the parent. Organisms evolved to specialize in large or small gametes, precursors to eggs and sperm.
A single footprint left by a cat-sized dinosaur around 100 million years ago has been discovered in China by an international team of palaeontologists.
Research from the University of Kansas into the genomes of the American pine marten and Pacific pine marten -- weasel-like mammals that range today from Alaska to the American Southwest -- could shed light on how the first humans populated the Americas.
It is an old-standing theory in evolutionary ecology: animal species on islands have the tendency to become either giants or dwarfs in comparison to mainland relatives. Since its formulation in the 1960s, however, the 'island rule' has been severely debated by scientists. Researchers solved this debate by analysing thousands of vertebrate species. They show that the island rule effects are widespread in mammals, birds and reptiles, but less evident in amphibians.
Researchers from the Max Planck Institute for Evolutionary Anthropology retrieved Neandertal nuclear DNA from cave deposits in northern Spain and southern Siberia, yielding new clues to the population history of Neandertals. With the advent of nuclear DNA analyses of sediments, similar studies at other sites can provide new insights into the deep human past that do not rely on the discovery of bones and teeth.
Mitochondrial DNA of archaic humans has been retrieved from cave sediments, but it has limited value for studying population relationships.
Over their entire late-Cretaceous reign, the total number of Tyrannosaurus rex that ever lived on Earth was roughly 2.5 billion individuals, according to a new study, which leveraged the relationship between body mass and population density observed in living animals to estimate the population traits of the iconic, long-extinct species.
With fossils few and far between, paleontologists have shied away from estimating the size of extinct populations. But UC Berkeley scientists decided to try, focusing on the North American predator T. rex. Using data from the latest fossil analyses, they concluded that some 20,000 adults likely roamed the continent at any one time, from Mexico to Canada. The species survived for perhaps 2.5 million years, which means that about 2.5 billion lived and died overall.