Kategori: Biology

Book Review: The Rise and Fall of the Dinosaurs by Steve Brusatte

Publicerat i Biology, dinosaurs, NatureMärkt , , , Lämna en kommentar
Various dinosaurs in a lush valley with waterfalls, forests, and an active volcano background.

Book summary:

In ”The Rise and Fall of the Dinosaurs”, palaeontologist Steve Brusatte tells the 200-million-year story of dinosaurs: From their small beginnings to their global dominance and sudden extinction. The book brings dinosaurs to life as dynamic, evolving animals rather than slow, primitive reptiles.

Dinosaurs first appeared after a massive extinction about 252 million years ago. At first, they were small and overshadowed by other reptiles, but environmental changes and new opportunities allowed them to diversify. During the Jurassic and Cretaceous periods, dinosaurs evolved into a stunning variety of forms: From enormous, long-necked herbivores to powerful predators like Tyrannosaurus rex (T-rex for the rest of this post).

One of the book’s most important insights is that birds are living dinosaurs. Fossil discoveries, especially feathered species, show that feathers and flight evolved gradually. This means dinosaurs never fully disappeared. They still exist today in the form of birds.

After ruling Earth for around 150 million years, most dinosaurs were wiped out 66 million years ago when a massive asteroid struck Earth, causing global climate collapse. Small bird-like dinosaurs survived, and their descendants continue to thrive today.

Bottom line: Dinosaurs weren’t just giant extinct creatures. They were adaptable survivors whose legacy still lives above us in the skies.

Why I read the book:

When I was a pre-schooler and primary school student, like many others, I loved dinosaurs and read many books about them. However, after turning twelve I had read nothing about these pre-histori creatures until I came across the book ”The Rise and Fall of the Dinosaurs” by Steve Brusatte.

To be honest, the main reason I decided to read it is that I now have the next generation of dinosaur-enthusiastic pre-schooler at home. I felt that I wanted to know more about dinosaurs to engage in meaningful and deeper conversations with my daughter about the science behind them. I wanted to talk to her not only about how dinosaurs were very big and cool animals, but also about deeper scientific concepts. This book has really helped me with this.

For example, my daughter and me had a conversation about how dinosaurs evolved into birds that are still around. This concept is today mentioned in most dinosaur books for pre-schoolers. (It was not when I was a child.) When my daughter asked me if T-rex turned into a bird, I could confidently answer that it was not T-rex himself, but a related species of biped, meat-eating dinosaurs, a cousin so to speak.

This turned into a discussion about what features T-rex and other biped, meat-eating dinosaurs had that we still see in birds today. Brusattes book really helped me with some similarities here, which I would not have known to mention to my daughter otherwise.

We came up with:

  • their feet look very similar
  • some biped, meat-eating dinosaurs had feathers
  • they lay eggs with hard shells
  • most biped, meat-eating dinosaurs could run very fast like some birds today (ostrich, emu, nandu, chicken)
  • caring for their young
  • fast growth

What I though if the book:

Despite originally reading it to keep up with my child’s ever-growing dinosaur knowledge, it turned out that I actually enjoyed this book very much and would recommend it to anyone who has an interest in science and nature. The following paragraphs describe why that is.

What I really liked about the book is how Brusatte blends his personal experiences foraging for fossils with the evolution of dinosaurs. He tells you about trips he took looking for fossils, trips to labs or even just having discussions with other scientists and fits this into the different periods that dinosaurs were around on Earth. Sometimes, this can feel a bit drawn out and slow, but for the most part it succeeds in bringing palaeontology to life. It also gives you a very good idea about what the work of a palaeontologist is like today and what tools they have at their disposal when researching pre-historic life.

Brusatte also succeeds at bringing scenes from the world of the dinosaurs to live. I will never forget the scene where he describes a T-rex hunting some Edmontosaurus on a riverbank. It really feels like you are there watching it together with the poor Triceratops on the other side of the river. The same goes for the scene describing how a pack of T-rexes would have experienced the asteroid impact that caused their extinction 66 million years ago.

I was first a bit sceptical that a whole chapter was dedicated solely to T-rex. I felt a bit like: ”Have we not heard enough of T-rex? Everyone knows about him.” But I learned a lot of new facts about T-rex (that I can share with my dinosaur-crazy pre-schooler) and am glad now I did not jump this chapter like I first wanted to. For example, I had no idea palaeontologists believe they may have lived in packs. Nor did I know that they are assumed to have been quite smart, about as smart as chimpanzees based on the ratio of their brain size versus body size!

I also loved how Brusatte covers the evolution and changes of ecosystems during the time of the dinosaurs. This is no easy feat considering the number of changes taking place over this time like the supercontinent Pangaea slowly breaking up into the continents we know today. It also reminded me how short the time is that we humans have been around. Our genus ”Homo” has only been around for 2 to 3 million years and our species ”Homo sapiens” only for a meagre 300 000 years. That is nothing compared to how long dinosaurs ruled the Earth from the late Triassic to the late Cretaceous, for more than 150 million years.

Wildlife Feeding Traces: What to Look For

Publicerat i Biology, Experiments at Home, Experiments/practicals for science lessons, Nature, Science Reading ExercisesMärkt , , , , , Lämna en kommentar

When taking a walk in the forest in early spring you can find many feeding traces of different animals. Join us in exploring some of them.

1 Traces left on trees

Deer, rabbits and hares all feast on the bark of trees during the winter months when grass and other plants do not grow well. But they leave different clues on trees that help us tell them apart.

Deer are quite tall, so they can reach higher parts of a tree. When deer eat, they often tear the bark with their mouths. This can leave rough, jagged edges on the tree. You might also see damage higher up, about as tall as your chest or even above your head. In addition, roe deer and red deer normally pull of strips of bark, while fallow deer are more content to nibble.

The image below shows a tree which had some of its bark most likely stripped of by a roe deer during winter. The dark colour shows that the tree has begun to heal in this part.

Rabbits and hares are much smaller than deer, so they can only reach low parts of a tree. They have very sharp front teeth, and they nibble neatly. This means the bark or twigs they eat often look cleanly cut, almost like they were snipped with tiny scissors. The damage is usually close to the ground.

This image shows the damage in the bark close to the ground which means that it may have been eaten by a rabbit or hare.

In summary, if the tree is damaged high up with rough edges, it was likely a deer. If the damage is low down with neat, tidy bites, it was probably a rabbit or a hare.

2 Traces left by wild boar

Wild boar leave very noticeable signs when they search for food in the forest.

They use their strong snouts to dig in the ground. This is called “rooting.” When they do this, they turn over the soil looking for roots, insects, worms, and bulbs. The ground can look messy, with patches of earth all churned up, almost like it has been ploughed.

You might also see small holes and uneven ground where they have been digging. Sometimes large areas are disturbed, not just one spot.

Wild boar can also leave footprints. Their tracks look a bit like a deer’s, but they are rounder and wider. If the ground is soft, you may see many of these prints together.

So, if you see torn-up soil, lots of digging marks, and hoof prints in the forest, a wild boar has probably been there looking for food.

The image below shows a small area in a forest where wild boar have rooted for food.

3 Traces left on gnawed cones

In the forest, you can often find eaten spruce cones on the ground. By looking closely, you can tell which animal has been feeding on them.

A squirrel leaves quite a tidy cone behind. It holds the cone and nibbles off the scales one by one. When it is finished, mostly the middle part, called the core, is left. Squirrels normally leave some scales at the tip of the cone where they have been holding it. The image below shows a cone left by a squirrel under a tree. You can even see some scales around it on the ground.

A wood mouse eats in a different way. It strips the cone of every last scale and only the clean core is left, which may almost just look like a stick which can be seen in the image below.

Birds like woodpeckers and nuthatches have a special way of eating cones. They often wedge the cone into a crack in the bark of a tree to hold it still. Then they peck at it to get the seeds out. The cone may look pecked and broken, with rough marks. Sometimes you can even find the place in the tree where the cone was held, called a “cone anvil.”

So, a clean, stripped core is likely from a wood mouse, a cone with scales left at the top from a squirrel and a pecked cone, often near a tree crack, from a bird like a woodpecker or nuthatch.

Godzilla Gummy Bears by Osmosis

Publicerat i Biology, Experiments at Home, Experiments/practicals for science lessonsLämna en kommentar

You will need

  • 3 clear glasses or jars
  • 1 spoon
  • 2 cups of water
  • ½ cup of sugar
  • 1 package of gummy bears
  • 1 cup of juice
  • Post-it notes or pieces of paper and a pen for labelling

What to do

  1. Set three glasses or jars on the counter.
  2. Label one glass “water”, one “sugar water” and one “juice”
  3. Pour one cup of water into the glasses labelled “water” and “sugar water”.
  4. Pour one cup of juice into the last empty glass labelled “juice”.
  5. Add ½ cup of sugar to glass labelled “sugar water” and stir for 5 minutes.
  6. Put one gummy bear into each glass. Keep one gummy bear for comparison.
  7. Put the glasses in the fridge and leave the gummy bears to soak overnight.
  8. The next day use a spoon to take each gummy bear out of its glass.
  9. Compare the gummy bears to the one you left outside. What happened to them? You can even use a ruler to measure the gummy bears.
  10. All gummy bears are safe to eat. Compare how they feel when you eat them.

Background

Each liquid contained more water and less sugar than the gummy bears. The water went into the gummy bears to balance out the amount of water between the bears and the solution. This movement of water from a place with lots of water to a place with less water is called osmosis. For example, plant roots use osmosis to take up water from the soil.

The gummy bears swelled up because water moved into them through osmosis. The larger the bear, the more water moved into it. How was osmosis different for the three liquids used?

You can watch a short video of this experiment here:

Home Experiment: Colour Changing Celery

Publicerat i Biology, Experiments at Home, Experiments/practicals for science lessonsLämna en kommentar

You will need

  • 2 tall, clear glasses or jars
  • Knife
  • Food colouring (you choose the colour)
  • 2 long celery sticks
  • Water

What to do

  1. Fill two tall, clear glasses with water.
  2. Put 3 – 4 drops of food colouring in each glass.
  3. Wash two long celery sticks.
  4. Use the knife to cut the bottom 3 cm and top 5 cm off each celery sticks.
  5. Place one celery stick into a glass of coloured water immediately. There should be at least 3 cm of celery sticking up above the water.
  6. Set the other celery stick on the counter to dry for 30 minutes.
  7. After 30 minutes, place the second celery stick into the second glass of coloured water. There should be at least 3 cm of celery sticking up above the water.
  8. Let both celery sticks soak overnight.
  9. Observe what happens over the next two days.

Background

Water is very important for plants. They use it for photosynthesis in their leaves to make their own food. The water that is used up in the leaves is taken from the soil and moves up through the plants – defying gravity! This movement of water in plants is called “transpiration”.

In this experiment, you can observe the water movement by tracking the coloured water in your celery. Do you think water movement in plants works better in dry or wet plants?

You can watch a short video with this experiment here:

Eradicating polio. We are almost there!

Publicerat i Biology, Health and DiseaseLämna en kommentar

When I got my vaccinations as a child, there was one particular immunisation that I still remember today. Unlike all other vaccines it was not administered as an injection (which I hated and am still squirmish about today). Instead, the doctor just put a few sweet, sugary drops in my mouth and told me to swallow them. This was my polio vaccination.

I still remember five-year old me thinking: Was that it already? Where is the syringe? Maybe they are trying to trick me and will sting me later?

A girl is receiving her oral polio vaccine (OPV) developed by Albert Sabin.

Polio is caused by a virus that is spread from person to person. About 72 % of individuals who are infected with polio do not get ill at all. The rest often show flu-like symptoms like fever, tiredness, a sore throat or headache.

In a small proportion of patients, the polio virus moves into the spinal cord and nervous system. This can cause meningitis (an infection in the covering of the spinal cord and brain) and paralysis (the inability to move arms and/or legs). Paralysis, the most dreaded symptom, occurs in about 1 in 200 polio cases according to World Health Organization (WHO) estimates.

A person can die of polio if the paralysis includes a muscle called the ”diaphragm” which is located below the lungs. When the diaphragm muscle moves down the lungs fill with air. The air is pushed out of the lungs when the muscle moves up. If the diaphragm is paralysed patients loose the ability to breathe and suffocate.

The respiratory tract including the lungs and the diaphragm. The diaphragm is the muscle that fills the lungs with air when moving down and pushes air out of the lungs when moving up.

The only way to save these patients’ life is to put them inside a machine called an ”Iron Lung” which breathes for them. This large apparatus encloses the whole body, leaving only the patient’s head outside. It uses pressure to inflate and deflate the lungs enabling the individual to breathe.

Staff in Rhode Island hospital (US) examine a patient in an Iron Lung during a polio outbreak in 1960.

When recovering from polio some patients regain the use of their muscles and are be able to breathe and walk again. However, others never recover. Many have to continue using wheelchairs. Others spend the rest of their lives locked inside Iron Lungs.

Due to these horrible consequences, people in the Western world used to be terrified of polio in the first half of the 20th century. During local polio outbreaks, schools as well as places of worship would close and large gatherings were prohibited. Steps that sound only too familiar to today’s Covid-19 measures.

Another similarity between the two diseases is that many individuals do not get ill or only exhibit very mild symptoms which enables the wide spread of the disease. At the same time, other patients are hit very hard, die or suffer long-term repercussions. For polio, it was impossible to predict who would walk away with a light headache and who would have to spend the rest of their lives inside an Iron Lung.

In addition, as for Covid-19, there was an intense race to find a vaccine against polio. The first inactivated polio vaccine (IPV), which is given as an injection in arms or legs, developed by Jonas Salk, was approved 1955. Another oral polio vaccine (OPV), invented by Albert Sabin, came into use 1961. The latter was the vaccine that I received as a six-year old swallowing the sweet, sugary drops.

The introduction of the two polio vaccines was a huge success leading to the eradication of polio in large parts of the world. There have not been any new polio cases in the US since 1979 and in the UK since 1984. The Americas and the Western Pacific region were declared polio-free in 2000, India followed in 2014.

The latest part of the world to eradicate polio is Africa which has only been anounced recently, 25 August 2020, about seven years after the last new case was registered in Nigeria.

Only two countries remain were polio is still active, Pakistan and Afghanistan and eradicating the disease there seems to be only a question of time. We are almost there!

The large scale eradication of polio has been possible thanks to the vaccination programs of the WHO, Unicef and their partners. If you want to make a contribution to eradicating polio completely, you can donate polio vaccines through Unicef’s Online Shop.

The story of the eradication of polio gives hope that we will also be able to stop Covid-19. As with polio, much will depend on the development and use of vaccines. The images of rooms crammed with children in Iron Lungs are history today. The images of overfilled intensive care units with patients on ventilators will be history some day too, hopefully soon.

Women in Science: Barbara McClintock and the Discovery of Jumping Genes

Publicerat i Biology, Women in ScienceLämna en kommentar

Image: Barbara McClintock in her laboratory in 1947. Credit: Smithsonian Institution.

Barbara McClintock was born 118 years ago, 16 June 1902, in Hartford, Connecticut (US). The girl showed great interest in science and research already from a young age. However, her family had little money and was skeptical. They thought that it was better for her to marry and be financially secure.

Nevertheless, her father, a physician, supported her wishes in the end and in 1919, McClintock started a degree in Biology at Cornell University, New York (US). Six years later, she received her Master’s degree and in 1927 her PhD in genetics and zoology.

During her PhD studies, McClintock started the research that would shape her entire career. She began investigating the DNA of corn. For this work, microscopes and colouring techniques were used to identify and analyse individual corn chromosomes. (= long strands of DNA found in each living cell). In 1933, McClintock and her colleague, Harriet Creighton, published important results showing that chromosomes are the basis of genetics.

We need to keep in mind that McClintock conducted these experiments long before the structure of DNA was even discovered in 1952. This gives us an idea about how difficult and sophisticated her work must have been.

After a spell at the University of Missouri (1936-1941), McClintock moved to Long Island, New York to work at the Cold Spring Harbor Laboratory. She would stay for the rest of her professional life and conduct her most important research here.

In the 1940s and 50s, McClintock experimented with the colours of kernels on corn. This work led to the discovery that genetic information is not fixed. McClintock isolated two genes (= short sections of DNA) that controlled kernel colour and showed that they could move along a chromosome to different places. She also proved that these changes could affect neighbouring genes on the chromosome.

In 1983, McClintock received the Nobel Prize in Physiology or Medicine ”for her discovery of mobile genetic elements”. Popular science would come to call these moving genetic elements ”jumping genes”.

Barbara McClintock died 2 September 1992 in Huntington, New York (US).

Reading Exercise: Gene Mutations

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Mutations

What do the squirrel and the tulip have in common?

Both have a mutation in the gene that codes for the protein responsible for their colour. The mutation causes the squirrel to be white and have red eyes. This condition is also called “albinism”. The tulip has a mutation in only one petal giving half of it a yellow colour.

A mutation is a change in a gene that creates a new version of the gene or allele. Mutations happen when there is a mistake in copying DNA during cell division.

For example, one base in a DNA sequence might be replaced with another, a bit like typing the wrong letter in a word. This can happen naturally, but is more likely to happen if DNA has been damaged by radiation or certain chemicals.

The change in the body caused by a mutation can be either positive, negative or have no effect at all. Most of the time mutations only have a small or no effect on the proteins that are produced and do not change how the body works.

The Human Genome Project

In 2003, the first complete human genome was decoded by the Human Genome Project. This project involved many scientists from different countries and produced the map of 3.3 billion base pairs in one set of 46 chromosomes. Your genome contains all the DNA that is found inside your cells.

Further work showed that 99 % of DNA is the same for very human. Mapping a person’s genome can show their risk for developing certain diseases like cancer. It can also help to identify which medicine might be best to treat that person. In addition, mapping the genome can provide information about which genetic disorders someone could pass on to their children.

Questions

  1. What is a mutation and how does it occur?
  2. Mutations happen naturally, but what makes them more likely to occur?
  3. Are mutations positive, negative or none of the two?
  4. Looking at the squirrel, is the mutation affecting its colour positive or negative? Why? (Tip: Think about predators.)
  5. Looking at the tulip, is the mutation affecting its colour positive or negative? Why? (Remember, that the tulip needs to attract butterflies and bees.)
  6. What was the Human Genome Project?
  7. What is a genome?
  8. How much percent of DNA is the same for every human?
  9. Give three advantages of mapping a person’s genome.

Reading Exercise: What are Alleles?

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Chromosomes are found inside the nucleus of cells and consist of long strands of DNA. Each human cell has 46 chromosomes (23 pairs), apart from gametes (sex cells) which have only 23.

You can think of chromosomes as a set of books. Each book (chromosome) contains a set of instructions (genes). All of the books together contain all the instructions needed to make a certain organism (a living thing), for example a human or a flower.

There are always two copies of the same gene in an organism because chromosomes come in pairs. These two versions of the same gene are called alleles.

The two alleles for one characteristic do not have to be the same. They can be different. If both alleles for one gene are the same, they are homozygous (from homo = the same). If the alleles are different, they are heterozygous (from hetero = different).

For example, everyone has two alleles of the gene that decides eye colour. If someone has brown eyes and is homozygous for that gene, they will have two alleles for brown eyes. We can see this for individual B in the middle of the image..

A person could also have brown eyes and be heterozygous for that gene. They have one allele for brown eyes and another allele for blue eyes. We can see this for individual A to the left in the image. The reason that this person has brown eyes is that alleles can be either dominant or recessive.

The gene for brown eyes is dominant and we will always see this characteristic, no matter what other gene is present. The gene for blue eyes is recessive and we only see it when the dominant gene for brown eyes is not present. We can see this for individual C to the right in the image.

Characteristics that we see on the outside are called the phenotype. The characteristics in our genes are called the genotype. Phenotype and genotype can be slightly different. In our example we have seen that someone can have brown eyes as their phenotype, but both brown and blue eyes in their genotype.

Questions

  1. What are chromosomes and where are they found?
  2. What are alleles?
  3. What is meant by homozygous?
  4. What is meant by heterozygous?
  5. What is meant by dominant?
  6. What is meant by recessive?
  7. Why does a person have brown eyes even when they have genes for both brown and blue eyes?
  8. What is meant by phenotype?
  9. What is meant by genotype?
  10. What is the phenotype (= the colour seen on the outside) of a rose that is homozygous and has two dominant alleles for red colour?
  11. What is the phenotype of a rose that is homozygous and has two recessive alleles for white colour?
  12. What is the phenotype of a rose that is heterozygous and has one dominant allele for red colour and one recessive allele for white colour?

Reading Exercise: The Structure of DNA

Publicerat i Biology, Science Reading ExercisesLämna en kommentar

DNA is found inside the nucleus of each cell. One very long, coiled up molecule of DNA is called a chromosome. Human cells have 46 chromosomes in total.

Each DNA molecule contains two strands that are connected by a pair of substances called bases. It looks like a ladder, where the bases form the rungs. In addition, the ladder is wound and looks a bit like a spiral staircase. We call this wound-ladder structure of DNA a “double helix”.

This double helix structure of DNA was discovered by the British scientists James Watson and Francis Crick who received the Nobel Prize for their work in 1962.

There are four bases in DNA, adenine, thymine, cytosine and guanine, normally just called A, T, C and G. When forming pairs to make the rungs of the ladder, A always pairs with T and C with G. We call this complementary base pairs. The base pairs are held together by a weak attraction called hydrogen bonding.

Furthermore, each base is attached to a sugar which in turn bonds to a phosphate group. The sugars and phosphate form the backbone of the DNA strands.

A gene is one section of DNA that codes for one single characteristic or protein. We all have very small differences in our genes caused by slightly different orders of the bases in our DNA. This means that everyone’s DNA is unique. It allows scientists to match DNA from cells to specific people. For example, it helps scientists to find out how people are related or it can be used by forensic scientists to identify criminals.

Questions

  1. Where is DNA found?
  2. What is a chromosome? How many chromosomes do humans have?
  3. What does the structure of DNA look like? What do we call it?
  4. Who discovered the structure of DNA?
  5. Name the four bases in DNA.
  6. What is complimentary base pairing?
  7. What holds the base pairs together?
  8. What is a gene?
  9. Why is everyone’s DNA unique?
  10. How can the knowledge that everyone’s DNA is unique help scientists?

Debunking the myth of stinging nettles and dock leaves

Publicerat i Biology, Chemistry, NatureLämna en kommentar

Image credit: Copyright by Kenneth Allen. CC BY-SA 2.0. The image shows stinging nettle on the left and dock leaf on the right.

It is the 2020 Corona virus lockdown and I am teaching online from home. Trying to keep things a bit interesting I am putting together small experiments to do at home. While thinking about possible experiments for the topic ”Acids and Alkalis”, I remember something I was taught myself in primary school. The sap of dock leaves is supposed to relieve the symptoms of nettle stings.

Me and many other children around the world were taught that stinging nettles sting because their poison contains acids. The sap of dock leaves is supposed to help because it is alkaline and neutralizes (cancels out) the nettle’s acid.

Perfect! I thought and was very excited to have found a great activity for the children. Finding stinging nettles and dock leaves and investigating their properties at home.

However, I did some further reading and quickly realized that I would not be able to use this activity.

The leaves of stinging nettles are covered in tiny hairs. When you brush against them their tip breaks of and they turn into tiny needles injecting the venom into your skin. It is true that the venom contains acids like formic acid oxalic acid and tartaric acid. Nevertheless, scientists argue that their concentrations are too low to cause any pain.

Today the bad guys of nettle stings are believed to be three compounds that are found in our own bodies as well. Serotonin, acetylcholine and histamine. Serotonin and acetylcholine are produced by our nervous system where they carry messages between nerve cells. But when injected directly into our skin, they cause irritation and pain. Histamine is probably the worst of the trio, causing inflammation and allergic reactions to the skin. The effect or nettle stings is most likely due to a nasty combination of all three. However, in some nettle species tartaric acid and oxalic acid are thought to at least contribute to a longer duration of the pain.

Now we know that the pain and itching of nettle stings is not really caused by acids at all. But what about the alkali part? Is dock leaf sap really alkaline? The answer is no. It has also been suggested that dock leaves may contain antihistamines to cancel out the effect of the histamines, but there is no evidence for this either.

The effect of dock leaves might simply by attributed to the sap cooling the irritated skin or a placebo effect. However, there is some evidence that dock leaves could contain a chemical that reduces the effect of serotonin in the nettle venom.