Browsing Tag: TEDEducation

    The secret lives of baby fish – Amy McDermott
    Articles, Blog

    The secret lives of baby fish – Amy McDermott

    October 9, 2019


    What you’re looking at
    isn’t some weird x-ray. It’s actually a baby yellow tang surgeonfish
    at two months old. And you thought your childhood
    was awkward. But here is the same fish as an adult, a beautiful inhabitant of the
    Indian and Pacific Oceans’ coral reefs and one of the most popular captive fish
    for salt water aquariums. Of the 27,000 known fish species,
    over a quarter live on coral reefs that make up less than 1%
    of the Earth’s surface. But prior to settling down in this
    diverse tropical environment, baby coral reef fish face the difficult
    process of growing up on their own, undergoing drastic changes,
    and the journey of a lifetime before they find that reef to call home. The life cycle for most of these fish begins when their parents spew
    sperm and eggs into the water column. This can happen daily, seasonally,
    or yearly depending on the species, generally following lunar or
    seasonal tidal patterns. Left to their fate, the fertilized eggs
    drift with the currents, and millions of baby larvae
    hatch into the world. When they first emerge,
    the larvae are tiny and vulnerable. Some don’t even have gills yet
    and must absorb oxygen directly from the water
    through their tissue-thin skin. They may float in the water column
    anywhere from minutes to months, sometimes drifting thousands of miles
    across vast oceans, far from the reefs where they were born. Along the way, they must
    successfully avoid predators, obtain food, and ride the right currents
    to find their way to a suitable adult habitat, which might as well be a needle
    in vast haystack of ocean. So, how did they accomplish this feat? Until recently, marine biologists thought of
    larval fish as largely passive drifters, dispersed by ocean currents
    to distant locales. But in the last 20 years,
    new research has suggested that larvae may not be
    as helpless as they seem, and are capable of taking
    their fate in their own fins to maximize their chances of survival. The larvae of many species are
    unexpectedly strong swimmers, and can move vertically in the water column
    to place themselves in different water masses and preferentially ride certain currents. These fish may be choosing the best routes
    to their eventual homes. When searching for these homes, evidence suggests that larvae navigate
    via a complex suite of sensory systems, detecting both sound and smell. Odor, in particular, allows larvae to
    distinguish between different environments, even adjacent reefs, helping guide them toward their
    preferred adult habitats. Many will head for far-flung locales
    miles away from their birth place. But some will use smell
    and other sensory cues to navigate back to the reefs
    where they were born, even if they remain in the
    larval stage for months. So, what happens when larvae
    do find a suitable coral reef? Do they risk it all in one jump
    from the water column, hoping to land in exactly
    the right spot to settle down and metamorphose into adults? Not exactly. Instead, larvae appear to have
    more of a bungee system. Larvae will drop down in the water column
    to check out a reef below. If conditions aren’t right,
    they can jump back up into higher water masses and ride on, chancing that the next reef
    they find will be a better fit. But this is the point
    where our knowledge ends. We don’t know the geographic movements
    of individual larva for most species. Nor do we know which exact environmental
    cues and behaviors they use to navigate to the reefs
    they will call home. But we do know that these tiny trekkers are more than the fragile
    and helpless creatures science once believed them to be. The secret lives of baby fish
    remain largely mysterious to us, unknown adventures waiting to be told.

    The Atlantic slave trade: What too few textbooks told you – Anthony Hazard
    Articles, Blog

    The Atlantic slave trade: What too few textbooks told you – Anthony Hazard

    August 23, 2019


    Slavery, the treatment of human beings as property,
    deprived of personal rights, has occurred in many forms
    throughout the world. But one institution stands out for
    both its global scale and its lasting legacy. The Atlantic slave trade, occurring from the late 15th
    to the mid 19th century and spanning three continents, forcibly brought more than 10 million Africans
    to the Americas. The impact it would leave affected
    not only these slaves and their descendants, but the economies and histories
    of large parts of the world. There had been centuries of contact
    between Europe and Africa via the Mediterranean. But the Atlantic slave trade
    began in the late 1400s with Portuguese colonies in West Africa, and Spanish settlement
    of the Americas shortly after. The crops grown in the new colonies,
    sugar cane, tobacco, and cotton, were labor intensive, and there were not enough settlers
    or indentured servants to cultivate all the new land. American Natives were enslaved,
    but many died from new diseases, while others effectively resisted. And so to meet the massive
    demand for labor, the Europeans looked to Africa. African slavery had existed
    for centuries in various forms. Some slaves were indentured servants, with a limited term
    and the chance to buy one’s freedom. Others were more like European serfs. In some societies, slaves could
    be part of a master’s family, own land, and even rise
    to positions of power. But when white captains came offering
    manufactured goods, weapons, and rum for slaves, African kings and merchants
    had little reason to hesitate. They viewed the people they sold
    not as fellow Africans but criminals, debtors,
    or prisoners of war from rival tribes. By selling them, kings enriched
    their own realms, and strengthened them
    against neighboring enemies. African kingdoms prospered
    from the slave trade, but meeting the European’s massive demand
    created intense competition. Slavery replaced other criminal sentences, and capturing slaves
    became a motivation for war, rather than its result. To defend themselves from slave raids, neighboring kingdoms
    needed European firearms, which they also bought with slaves. The slave trade had become an arms race, altering societies and economies
    across the continent. As for the slaves themselves,
    they faced unimaginable brutality. After being marched
    to slave forts on the coast, shaved to prevent lice, and branded, they were loaded onto ships
    bound for the Americas. About 20% of them
    would never see land again. Most captains of the day
    were tight packers, cramming as many men
    as possible below deck. While the lack of sanitation
    caused many to die of disease, and others were thrown
    overboard for being sick, or as discipline, the captain’s ensured their profits
    by cutting off slave’s ears as proof of purchase. Some captives took matters
    into their own hands. Many inland Africans
    had never seen whites before, and thought them to be cannibals, constantly taking people away
    and returning for more. Afraid of being eaten,
    or just to avoid further suffering, they committed suicide
    or starved themselves, believing that in death,
    their souls would return home. Those who survived
    were completley dehumanized, treated as mere cargo. Women and children were kept above deck
    and abused by the crew, while the men were made to perform dances in order to keep them exercised
    and curb rebellion. What happened to those Africans
    who reached the New World and how the legacy of slavery
    still affects their descendants today is fairly well known. But what is not often discussed is the effect that the Atlantic slave trade
    had on Africa’s future. Not only did the continent lose
    tens of millions of its able-bodied population, but because most of the slaves
    taken were men, the long-term demographic
    effect was even greater. When the slave trade was finally
    outlawed in the Americas and Europe, the African kingdoms whose economies
    it had come to dominate collapsed, leaving them open
    to conquest and colonization. And the increased competition
    and influx of European weapons fueled warfare and instability
    that continues to this day. The Atlantic slave trade also contributed
    to the development of racist ideology. Most African slavery had no deeper reason
    than legal punishment or intertribal warfare, but the Europeans
    who preached a universal religion, and who had long ago
    outlawed enslaving fellow Christians, needed justification for a practice so obviously at odds
    with their ideals of equality. So they claimed that
    Africans were biologically inferior and destined to be slaves, making great efforts
    to justify this theory. Thus, slavery in Europe and the Americas
    acquired a racial basis, making it impossible for slaves
    and their future descendants to attain equal status in society. In all of these ways, the Atlantic slave trade
    was an injustice on a massive scale whose impact has continued
    long after its abolition.