“History of Life on Earth”

Have you ever wondered about when the earth was formed or how old is the earth right now? Well, I don’t even know about this too. But after this round of STEM class which is the last round of 2019, I have learned about these things called “History of Life on Earth”. Earth has formed about 4.6 billion years ago but first life just started to appear on Earth about 4 billion years ago. The first life forms were microscopic and single-celled organisms. From this simple start, we can see the diversity of life today. The tool that helps us to understand the history of Earth and its life is the geologic time scale. It divides Earth’s history into Supereon, Eons, Eras, and Periods just like in the picture below. These divisions are based on major changes in geology, climate, and the evolution of life

Geologic Time Scale

Geologic time scale

Precambrian – 4.6 billion Ago

(The Precambrian was originally defined as the era that predated the emergence of life in the Cambrian Period. It is now known, however, that life on Earth began by the early Archean and that fossilized organisms became more and more abundant throughout Precambrian time.)

  • Hadean – 4.6 billion Ago – When the earth starts to form, when earth still hit by an asteroid, overall earth on this eon is a hot rock. In the Hadean Eon, the heat is 3 times as high as it is today which is temperature is too high to sustain life. 
    • Archean – 3.8 billion Ago – When Earth’s climate becomes more stable and cool down enough to create continents, This eon start, oxygen is starting to form, when oxygen mixed with iron in the oceans and rusted collect on the seafloor.
    •  Proterozoic – 2.5 billion Ago – In Proterozoic, Earth is completely frozen. During this eon, life began to evolve into more complex organisms. Proterozoic is an eon when cyanobacteria produced oxygen, iron and methane were oxidized, and life emerged in the late period on the bottom of the sea. Several very server ice ages occurred in Proterozoic. 
  • Phanerozoic – 544 million Ago (The Phanerozoic Eon is a period during which abundant animal and plant life have existed.)
    • Paleozoic – 544 million Ago (This eon is the best known as the explosion of life on earth, this Era is after the Proterozoic when life began and this era is where life start to grow more and more) 
      • Cambrian 544 million Ago
        • The Cambrian Period was the largest diversification of life in Earth’s history. A new life started in the ocean then moved to land. Life got more diverse in the oceans in the age of fish. Eventually, life evolved on land in the age of amphibians.
      • Ordovician 505 million Ago
        • The Ordovician Period was when a rich variety of marine life flourished in the vast seas and the first primitive plants began to appear on land. Most of the world’s landmasses came together to create the supercontinent of Gondwana, which included the continents of Africa, South America, Antarctica, and Australia. 
      • Silurian 440 million Ago
        • Silurian Period is when animals and plants finally emerge on land. The growth of corals and other marine organisms was stoked by oceans teeming with tiny planktonic creatures. 
      • Devonian 410 million Ago
        • Devonian is a period that is known as the Age of Fishes and also a period that forests and the coiled shell-bearing marine organisms known as ammonites fossils first appeared.  There are several animals that live in this period including wingless insects and the earliest arachnids. 
      • Carboniferous 360 million Ago
        • The Carboniferous Period is also known as the Age of Amphibians. And the climate of the Carboniferous Period was quite uniform (there were no distinct seasons) and it was more humid and tropical than our present-day climate. In this period, there are a lot of and animals included primitive amphibians, reptiles (which first appeared in the Upper Carboniferous), spiders, millipedes, land snails, scorpions, enormous dragonflies, and more than 800 kinds of cockroaches.
      • Permian 290 million Ago
        • The Permian period, which is the last period of the Phanerozoic, which ended in the largest mass extinction the Earth has ever known, began about 299 million years ago. The emerging supercontinent of Pangaea presented severe extremes of climate and environment due to its vast size.
    • Mesozoic – 245 million Ago (The Mesozoic Era is the age of the dinosaurs and lasted almost 180 million years from approximately 250 to 65 million years ago. This era includes 3 well known periods called the Triassic, Jurassic, and Cretaceous periods. A mass-extinction marked the beginning and end of the Mesozoic Era.)
      • Triassic 245 million Ago
        • Triassic is about violent volcanic eruptions, climate change, or perhaps a fatal run-in with a comet or asteroid.
      • Jurassic 200 million Ago
        • Jurassic is about DINOSAURS, BIRDS, AND rodents. Crumbling landmasses and inland seas. Sea monsters, sharks, and blood-red plankton. Forests of ferns, cycads, and conifers. Warm, moist, tropical breezes.
      • Cretaceous 145 million Ago
        • The Cretaceous picked up where the Jurassic left off: Gigantic sauropods led parades of dinosaurs through the forests, over the plains, and along the coasts; long-necked and toothy marine reptiles terrorized fish, ammonites, and mollusks in the seas; pterosaurs and hairy-feathered birds filled the skies. But as the continents spread, the ocean currents churned with ever more vigor. After a temperature spike in the mid-Cretaceous, the climate began to cool, and the tenor changed.
    • Cenozoic – 65 million from Present (The Cenozoic Era is also known as the Age of Mammals because of the extinction of many groups of giant mammals, allowing smaller species to thrive and diversify because their predators no longer existed. Due to the large span of time covered by the period, it is beneficial to discuss the animal population by the milestone of the era rather than in generalities.)
      • Tertiary 65 million
        • Tertiary was the period of mammals. By the beginning of the Tertiary, the supercontinent of Pangea had been fragmenting for more than 100 million years, and the geometry of the continents and oceans had assumed an essentially modern aspect with several notable exceptions. 
      • Quaternary 1.8 million
        • The Quaternary Period has involved dramatic climate changes, which affected food resources and brought about the extinction of many species. The period also saw the rise of a new predator: man.

“Cells are the building blocks of life”               

STEM is a subject that requires a lot of work in order to learn and know more about it. It is very challenging for me to learn science vocabulary. I use lots of my time to read more about the topic and find the meaning of the vocabulary that I don’t understand. Nowadays, I feel like I better catch up with all the work. RALPH WALDO EMERSON said, “LIFE IS A JOURNEY, NOT A DESTINATION”. This means that the process of learning is more important than the end goal. The best way to be a successful person to study hard. This term we are learning about Cell, which is the structure of every living organism. Cells are the building blocks of life. Cells have divided into two different types either prokaryotic cells, which lack a nucleus, or eukaryotic cells, which have a nucleus. But all cells must contain a cell membrane, cytoplasm, DNA, and ribosomes. As we learn, we are focusing on two different cells which are animal cell and plant cell. The difference between these two cells is because plant cell has a Cell wall, large vacuole and plastid compare to the animal cell don’t have. In conclusion, I enjoy learning about cells because it is interesting to learn and see it under the microscope. I’m excited to get to know more about these topics and it would be a very awesome thing if I could learn more deeply into it.


Newton’s Laws of Motion

For this last round, in STEM class we learn about Newton’s Laws of Motion. How many Newton’s Laws of motion. There are 3 different laws of motion. Newton’s first law said that an object’s motion will not change unless an unbalanced force acts on the object. And if the object is at rest, it will stay at rest. If the object is in motion, it will stay in motion and Newton’s second law is the relationships between these two factors and motion. And the last Newton’s law of motion which is Newton’s third law is that every action has an equal and opposite reaction it’s mean that forces always act in pairs. And the acceleration of an object equals the net force acting on the object divided by the object’s mass.


So now in Stem class, we learn about motion. What is motion? so motion can also be defined simply, as a change in position. In this lesson, we learn more about motion such as Distance, Direction, and a lot more. So  Distance is the length of the route between two points and Direction is just as important as a distance in describing motion. And also we learn about SI units too. SI units for distance is the meter but short distance may be measured by a centimeter and long distance may be measured by kilometer. 



Carbon Cycle

Carbon is cycled by combustions and animals, human, trees releasing and consuming carbon. There is one process that removes carbon dioxide from the air which is Photosynthesis. And there is more than one process that adds to the air such as Plants Respiration, Root Respiration, Animals Respiration, Dead Organism, Waste products and more. There are many human activities that disrupt the natural carbon cycle such as deforestation, transportation, farming, factory emission, burning trash and trees and using a plastic bag. To stop this human activity that disruption to the carbon cycle, we need to use the public bus, stop burning trash and trees, stop factory emission, start to stop using plastic and stop killing the animals. 


Chemical Bonding 

So now in stem class, we have learned about the Chemical Bonding. So chemical bond is a force of attractions between atoms and ion. In chemical bonding, they’re three type of that such as Ionic bonding, Covalent bonding, and metallic bonding. For example, Ionic bonding is the force of the attraction that holds together positive and negative. This picture below is showing the Ionic bonding.

Physical Science

Physical Science is the class that we study about Matter and energy including physic and chemistry. Our class we have one Website call CK12 that used to know more about our Topic. At this beginning of the year, we have studied about the matter and I don’t know what is matter but after I learn it I know it. So the matter is anything that has mass and volume. After we learn about the matter we also have learned about Atoms. A teacher has explained a lot about it like what is inside atoms. And we know a lot more about it. And I know that inside Atoms has Proton and Neutron and Electron. Proton has positive charge Neutron has no charge and Electron has a negative charge. Quark has to create Proton and Neutron and for Electron has created by Lepton. and there are six type of Quark and six type of Lepton.