# data[].attributes.headline
Life of Mammals - Revision session voice recording 17/04/2018

# data[].attributes.subject
Life of Mammals - Revision session voice recording 17/04/2018

# data[].attributes.headline
Keystone predator hypothesis (tutorial notes)

# data[].attributes.subject
Keystone predator hypothesis (tutorial notes)

# data[].attributes.headline
Rough PCE tutorial notes (predator-prey) 

# data[].attributes.subject
Rough PCE tutorial notes (predator-prey) 

# data[].attributes.body
May be some gaps, but rough notes for anyone who missed it.

# data[].attributes.body
Here you guys can post your revision notes, links to interesting articles and questions etc. Anonymously.

# data[].attributes.attachment_link.readable_text
Visuals Unlimited/NPL

It is not unusual for insect pests to feast on each other as well as on their staple veg, but it's now been shown that tomato plants can team up to directly push caterpillars into cannibalism.

"This is a new ecological mechanism of induced resistance that effectively changes the behaviour of the insects," says Richard Karban, who studies interactions between herbivores and their host plants at the University of California at Davis and was not involved in the study.

Herbivorous pests often turn on each other when their food is of poor quality or it runs out. And some plants are known to affect the behaviour of their pests by making them more predatory towards other species. But until now it was unclear whether plants could directly cause caterpillar cannibalism.

Integrative biologist John Orrock and his colleagues at the University of Wisconsin in Madison triggered a defensive reaction in tomato plants ( Solanum lycopersicum) by exposing them to various amounts of methyl jasmonate (MeJA). This is an airborne chemical that plants release to alert each other to danger from pests. When cued with MeJA, tomato plants respond by producing toxins that make them less nutritious to insects.

The researchers then allowed caterpillars of a common pest, the small mottled willow moth ( Spodoptera exigua), to attack the crop. Eight days later, they observed that plants more strongly cued with MeJA had lost less biomass compared with control plants or with ones that had received a weaker induction. This showed that the reaction was somehow effective at protecting the plants.

Cannibalism trigger

Next, the team wanted to test whether the plants' response was triggering cannibalistic behaviour in the caterpillars. So they cued tomato plants with MeJA and then fed leaves from cued plants and non-cued control plants to single caterpillars in containers that also contained a set number of dead caterpillars. Two days later, the team observed that caterpillars fed with leaves from the treated plants had turned onto the dead larvae earlier, and had eaten more of them, than those fed with leaves from control plants. The results are published in Nature Ecology & Evolution.

The caterpillars will always eat each other eventually, but the difference in timing is critical, says Orrock, "if plants can induce pests to eat each other earlier, there will be more of the plant left untouched". However, he also cautions that the cost to the plant of activating its defences is very high. "It is very possible that the plants will strike a balance and decide if the attack is serious enough to activate the defences."

Anurag Agrawal, who studies plant-animal interactions at Cornell University in Ithaca, New York, says that the study suggests that farmers could foster cannibalism as a pest-management strategy. "Nonetheless, under some field conditions, cannibals may be more fit than non-cannibals. So this is something to watch out for," he added, "We don't want to be encouraging super-pests".

# data[].attributes.attachment_link.description
Visuals Unlimited/NPL It is not unusual for insect pests to feast on each other as well as on their staple veg, but it's now been shown that tomato plants can team up to directly push caterpillars into cannibalism.

# data[].attributes.attachment_link.readable_text
Honey bees on every continent except Antarctica face significant exposure to neonicotinoid pesticides - chemicals that some studies suggest harm bees' health. Researchers who tested honey from nearly 200 sites worldwide found that 75% of their samples contained some level of the pesticides, according to a report published on 6 October in .

The study is the first attempt to quantify the presence of neonicotinoids in honey on a global scale using standardized methods. Nearly half of the samples tested contained levels of neonicotinoids at least as high as those thought, on the basis of previous research, to impair bees' brain function and slow the growth of their colonies. The study also found that 45% of the samples contained two or more types of neonicotinoid.

"It's not a surprise, in a sense, that we find neonicotinoids in honey. Anybody could have guessed that," says lead author Edward Mitchell, a biologist at the University of Neuchâtel in Switzerland. "What's original is using the same protocol. We now have a worldwide map of the situation."

The research provides additional context for the long-running debate over whether and how neonicotinoids affect bees' health. Some studies have suggested that exposure to neonicotinoids lowers honey bees' nutritional status and impairs their immunity. And in June, a paper published in Science reported that neonicotinoids lower honey bees' chances of survival during the winter, and threaten the queen in particular, which can affect reproduction.

To assess the scale of honey bees' exposure to neonicotinoids around the world, the authors of the new study collected honey from 198 sites on six continents through a citizen-science project. Then they tested those samples to determine the concentrations of five of the most commonly used neonicotinoids. Honey collected in North America had the highest proportion of samples containing at least one neonicotinoid, at 86%, with Asia (80%) and Europe (79%) close behind.

The extent of the contamination, even in honey from remote places - including islands in the middle of the Pacific Ocean and off the coast of West Africa - is surprising, says Amro Zayed, an insect researcher at York University, UK. The findings suggest that bees the world over are exposed to neonicotinoids constantly over generations, he says, which is worrying because the insects depend so heavily on honey for food. "It's one thing to go out to a restaurant and get a bad meal, but if you have your fridge at home contaminated with insecticides, that's an entirely different method of exposure," Zayed says.

Others say that the widespread presence of neonicotinoids in honey is to be expected, given how commonly the chemicals are used in staple crops such as canola and wheat, as well as in home gardens. "Yes, there is going to be long-term exposure, potentially, to neonics, but that doesn't say anything about the risk," says Chris Cutler, an entomologist at Dalhousie University in Halifax, Canada. "Just because it's there doesn't necessarily mean there's a problem."

Much of the debate about neocotinoids has focused on just this question: how problematic are the pesticides when bees are exposed to them at low levels, but over a long period of time? "One of the issues around assessing the impacts on bees has been the discussion of what a field-relevant level of exposure actually is," says Nigel Raine, a pollinator-health researcher at the University of Guelph in Canada. "This contributes toward that discussion substantially."

# data[].attributes.attachment_link.title
Controversial pesticides found in honey samples from six continents

# data[].attributes.attachment_link.description
Honey bees on every continent except Antarctica face significant exposure to neonicotinoid pesticides - chemicals that some studies suggest harm bees' health. Researchers who tested honey from nearly 200 sites worldwide found that 75% of their samples contained some level of the pesticides, according to a report published on 6 October in .

# data[].attributes.attachment_link.readable_text
Jurgen Freund/NPL/Getty

The mystery behind a dramatic fall in the number of leatherback sea-turtle ( Dermochelys coriacea) hatchlings in the US Virgin Islands remains unsolved, despite the latest efforts of researchers. Rising temperatures and changes in rainfall patterns - the top two suspects - don't seem to be connected to the decline, according to a study published on 4 October. The finding contradicts previous work, leaving researchers scratching their heads over what could be happening.

The latest study focused on a nesting beach in the Sandy Point National Wildlife Refuge on St Croix island in the Caribbean Sea. The researchers found that about 74% of the leatherback sea-turtle eggs laid there in 1990 hatched, but that rate had plummeted to 55% by 2010.

The study analysed detailed temperature and precipitation data at these nests over the 20 years, and found no corresponding trend in either climate-change factor that could fully account for the decline. The researchers reported their results in Royal Society Open Science.

Increases in temperature and more-erratic precipitation patterns do affect the nests, but they aren't the sole reason for the hatching declines, says Anthony Rafferty, a marine biologist at Monash University in Melbourne, Australia, and a study co-author.

This trend is especially confusing in light of the increase in the adult sea-turtle population. "The number of nesting females and the population size has been trending upwards at this site," Rafferty says. "But there's been a decrease in hatching success that we are worried about." That could have negative effects on leatherback populations within one or two decades, he says, when those hatchlings come of age.
Conundrum continues
"It's hard to say how much of that is happening because of climate change," says Vincent Saba, a climate scientist at the US National Oceanic and Atmospheric Administration in Princeton, New Jersey. He co-authored a 2015 study that did find a relationship between air temperature, precipitation patterns and declines in leatherback hatching success. That study examined data from 1982 to 2010 and looked at seasonal rainfall, unlike the latest paper, which analysed rainfall only during the nesting season. The study predicted that, by 2100, Sandy Point would have the most unfavourable climate conditions out of all leatherback nesting sites around the world.

"I like the study. They looked at the effect of climate in finer detail," says Pilar Santidrián Tomillo, a marine biologist and science director of the Leatherback Trust, based in Playa Grande, Costa Rica. She was a co-author on the 2015 study, and appreciates the fuller picture of what could be happening at Sandy Point that the most recent study has provided.

Sea-turtle eggs are exquisitely sensitive to climate because heat, carbon dioxide, oxygen and water all pass freely through their permeable shells. The surrounding temperatures determine the sex of the hatchlings: warmer conditions produce more females, whereas cooler conditions yield males. And rainfall can influence hatchling development and their ability to escape the nest, says Rafferty. Too little rain might mean that the sand is too dry for the young turtles to climb out of it; too much rain during the early stages of egg development might lead to a reduction in oxygen supplies to the growing embryo.

"I think changes in precipitation levels or patterns could explain the decline in hatching success partially, but there could be other reasons, too, like decline in fertility or increase in pollutants, for example," Santidrián Tomillo says.

Rafferty, who specializes in embryo research, now plans to look at how the age and health of a female sea turtle might affect her fertility, or where she lays her eggs.

# data[].attributes.attachment_link.title
Crash in sea-turtle births stumps ecologists

# data[].attributes.attachment_link.description
Jurgen Freund/NPL/Getty The mystery behind a dramatic fall in the number of leatherback sea-turtle ( Dermochelys coriacea) hatchlings in the US Virgin Islands remains unsolved, despite the latest efforts of researchers. Rising temperatures and changes in rainfall patterns - the top two suspects - don't seem to be connected to the decline, according to a study published on 4 October.

# data[].attributes.attachment_link.readable_text
Aged chimpanzees develop brain characteristics that are similar - but not identical - to those seen in early Alzheimer's disease in humans, researchers report on 1 August in Neurobiology of Aging ( M. K. Edler et al. Neurobiol. Aging http://dx.doi.org/10.1016/j.neurobiolaging.2017.07.006; 2017). The findings from humanity's closest relatives could help researchers to understand why people develop dementia, as well as suggest that caretakers of aging, captive chimpanzees watch them closely for behavioural changes.

Although most animals' cognitive abilities decline late in life, only people seem to develop Alzheimer's disease, which can result in severe dementia symptoms. The brains of people with Alzheimer's show several signs of the disease: plaques made of a protein called amyloid-β, tangles of a protein called tau and the loss of neurons. Humans were thought to be the only primates with brains that can contain plaques and tangles simultaneously - although one study did find both markers in a single chimp brain ( R. F. Rosen et al. J. Comp. Neurol. 509, 259-270; 2008).

Using a collection of chimpanzee brains that has been compiled over several decades, a team led by Mary Ann Raghanti, a biological anthropologist at Kent State University in Ohio, analysed the brains of 20 aged chimps that had died between 37 and 62 years of age. The team examined the brain regions that are damaged in people with Alzheimer's - such as the memory-forming hippocampus - and found that four of the preserved chimp brains contained both plaques and tangles. All 20 of the specimens contained 'pre-tangles', and blood vessels in several of the chimp brains contained amyloid-β. Because the protein is normally found outside of blood vessels in the human brain, this suggests that plaques may form in a different way in chimps.

"This is a really cool paper", says Elizabeth Head, a neuroscientist at the University of Kentucky in Lexington. Even if chimps never develop the symptoms of Alzheimer's, knowing that they spontaneously develop biological signs of the disease could yield useful information about its early stages and potentially how to prevent it, she says.

Lary Walker, an experimental neuropathologist at Emory University in Atlanta, Georgia, is also impressed with the study. The strength of the paper, he says, is that the large number of animals involved provide a good sample of the different ways in which chimp brains age.

The researchers were not able to link the biological changes in the chimps' brains to shifts in their behaviour later in life. The animals had lived in zoos, research labs and sanctuaries, and had, therefore, been exposed to different stimuli and undergone different cognitive tests.

Although severe dementia has never been observed in chimps, the presence of both plaques and tangles suggests that it could, says study co-author William Hopkins, a psychologist at Georgia State University in Atlanta. Given these findings, he says, those who look after chimps should actively monitor the cognitive health of ageing animals. In 2015, the United States effectively ended biomedical research on chimps, including magnetic resonance imaging scans, but Hopkins says that such scans could be useful for the aging population of animals retired from research facilities.

The sequences of amyloid-β and tau proteins are identical in humans and chimps. But it is possible that there is a factor protecting chimp brains from severe dementia. "They're missing something," Walker says of the chimps. One possibility, he adds, is that the amyloid-β and tau proteins may fold differently in chimps than in people.

Another difference could be the behaviour of a protein called APOE, which controls how amyloid-β aggregates into plaques. Humans have evolved several versions of the APOE gene, one of which - APOE4 - makes a person more likely to develop Alzheimer's. It is possible that evolution selected for the 'bad' version of APOE in people because it protects them from something else, such as a parasite, says Caleb Finch, who studies ageing at the University of Southern California in Los Angeles ( B. C. Trumble et al. FASEB J. 31, 1508-1515; 2017).

Raghanti says that the researchers are now counting the neurons in the chimp brains they studied to determine whether the cells are lost with age, and studying inflammation in the brains. Both neuron loss and inflammation seem to contribute to Alzheimer's in humans. "If we could identify the things that are similar and different in chimpanzees and humans, we can start to unlock why humans are so uniquely susceptible to this pathology," she says.

# data[].attributes.attachment_link.title
Chimpanzees are first animal shown to develop telltale markers of Alzheimer's disease

# data[].attributes.attachment_link.description
Aged chimpanzees develop brain characteristics that are similar - but not identical - to those seen in early Alzheimer's disease in humans, researchers report on 1 August in Neurobiology of Aging ( M. K. Edler et al. Neurobiol. Aging http://dx.doi.org/10.1016/j.neurobiolaging.2017.07.006; 2017).

# data[].attributes.attachment_link.description
Cladistics is now the most commonly used method to classify organisms. Why do we need to classify organisms? Well, consider the bewildering variety of organisms that have ever lived on Earth, from jellyfish to bacteria - that's what paleontologists do for a living.

# data[].attributes.attachment_link.readable_text
An effort to capture the few remaining vaquita porpoises in Mexico's Gulf of California will start next week.

Mexican authorities and an international group of experts say they will set out on Oct. 12 in small boats to find the elusive marine mammals with the assistance of trained dolphins.

Despite Mexico's campaign to help the species, which are the world's smallest and rarest type of porpoises, the number of remaining vaquitas is estimated to have dropped below 30.

Vaquitas are often caught in nets illegally set to catch totoaba fish, whose bladder is prized in China.

Mexico enacted a permanent ban on gillnet fishing in the northern Gulf of California earlier this year.

Related: Mexico invests up to $3 million dollars in Vaquita Sanctuary plan, U.S. trained dolphins will aide in search for endangered vaquita porpoises

# data[].attributes.attachment_link.title
On October 12, Mexico will begin capturing remaining Vaquita porpoises

# data[].attributes.attachment_link.description
An effort to capture the few remaining vaquita porpoises in Mexico's Gulf of California will start next week. Mexican authorities and an international group of experts say they will set out on Oct. 12 in small boats to find the elusive marine mammals with the assistance of trained dolphins.