new11

The primordial universe was almost perfectly homogeneous other than tiny quantum density fluctuations. Dark matter preserved these variations through gravitational forces at a time when ordinary matter could not form stable dense regions due to absorption of intense electromagnetic radiation. As the universe expanded, it cooled and the energy per photon decreased to the level at which matter could condense into the dense regions formed by dark matter. Without dark matter, structure would not have formed in the universe and there would be no cosmic web, galaxies, stars, planets, or life.

Back to top

Our galaxy consists of two disks of stars, a central bulge, a supermassive black hole, and interstellar medium which is the birthplace of new stars. And one more thing, 95% of its mass is the unseen dark matter which holds everything together gravitationally. Our galaxy formed from the merger of numerous smaller galaxies in a relatively less densely populated region of the universe.

Back to top

new13

Supernovas are massive stars that synthesize elements up to the iron group. When they explode, they synthesize additional elements and they enrich the interstellar medium with all of these elements. The molecular clouds in the interstellar medium are sites where later generations of stars form with their inheritance of metals.

Some supernovas leave neutron stars behind as remnants and in the case of binary star systems, some of the neutron stars merge by dispersing energy through gravity waves. These mergers synthesize many of the heavier elements that are not synthesized in supernovas. The interior of the Earth has retained much of its initial heat of formation due to the decay of radioactive elements like uranium and thorium. The heat flow drives convection in the opaque rocks of the mantle, producing plate tectonics, earthquakes, volcanoes, and the formation of islands and continents. Without neutron star mergers, the rock formations of the Grand Canyon would not exist. These movements also play a major role in climate and biogeochemical cycles. So neutron stars and the gravity waves that facilitated their mergers had profound effects on Earth and its geobiosphere.

Back to top

Our solar system has exactly one star which provides a steady output for any orbiting planets. It is small enough to live long enough for life to evolve on adjacent planets. It is not a giant star with excessive ultraviolet radiation, but it is large enough to produce a spectrum that is beneficial to organisms. It is a population I star which means it formed with enough metals to form rocky planets and molecular building blocks of life. It is located in a stable region in the galaxy.

Earth is located in the Goldilocks zone of our solar system. The interplanetary medium includes gas and dust essential for life. The influence of the moon fostered the evolution of complex life on Earth. The solar system has enough planets and other minor bodies to provide a few rare catastrophes that do not cause total annihilation, but causes enough mass extinction to open up ecological niches for an evolving biosphere.

Sunlight, climate, the water cycle, carbon cycle, rock cycles, plate tectonics, asteroids, and the elements of the geobiosphere are products of nuclear reactions in the sun, supernovas, neutron stars, and their decaying elements.

Water is essential to plate tectonics and life is essential to the retention of water on Earth.

Minerals and prebiotic organic molecules were abundant and widely distributed and prebiotic molecules and geochemical cycles and processes fostered the origin of life.

new21

new22

new23

new32

Cells are chemical factories that process and exchange molecules, energy, and information with other cells and their environment.

Cells provide six main functions https://sciencing.com/six-main-cell-functions-6891800.html.

Provide Structure and Support

A cell is the structural and functional unit of life. Each cell contains smaller organelles that perform various functions such as metabolism, transportation and secretion of substances. Because some cells perform specific functions, they have special modified structures. For example, red blood cells are the oxygen carriers in the body. They lack a nucleus to make more space for the oxygen-carrying pigment, hemoglobin. The various structures and organelles in a cell float in a liquid called the cytoplasm.

Like a classroom is made of bricks, every organism is made of cells. While some cells such as the collenchyma and sclerenchyma are specifically meant for structural support, all cells generally provide the structural basis of all organisms. For instance, skin is made up of a number of skin cells. Vascular plants have evolved a special tissue called xylem, which is made of cells that provide structural support.

Facilitate Growth Through Mitosis

In complex organisms, tissues grow by simple multiplication of cells. This takes place through the process of mitosis in which the parent cell breaks down to form two daughter cells identical to it. Mitosis is also the process through which simpler organisms reproduce and give rise to new organisms.

Allow Passive and Active Transport

Cells import nutrients to use in the various chemical processes that go on inside them. These processes produce waste which a cell needs to get rid of. Small molecules such as oxygen, carbon dioxide and ethanol get across the cell membrane through the process of simple diffusion. This is regulated with a concentration gradient across the cell membrane. This is known as passive transport. However, larger molecules, such as proteins and polysaccharides, go in and out of a cell through the process of active transport in which the cell uses vesicles to excrete or absorb larger molecules.

Produce Energy

An organism's survival depends upon the thousands of chemical reactions that cells carry out relentlessly. For these reactions, cells require energy. Most plants get this energy through the process of photosynthesis, whereas animals get their energy through a mechanism called respiration.

Create Metabolic Reactions

Metabolism includes all the chemical reactions that take place inside an organism to keep it alive. These reactions can be catabolic or anabolic. The process of energy production by breaking down molecules (glucose) is known as catabolism. Anabolic reactions, on the other hand, use energy to make bigger substances from simpler ones.

Aid in Reproduction

Reproduction is vital for the survival of a species. A cell helps in reproduction through the processes of mitosis (in more evolved organisms) and meiosis. In mitosis cells simply divide to form new cells. This is termed asexual reproduction. Meiosis takes place in gametes or reproductive cells where there is a mixing of genetic information. This causes daughter cells to be genetically different from the parent cells. Meiosis is a part of sexual reproduction.

new33

What do cells do? How do they do what they do? How did they evolve the ability to do what they do?

Cells must perform 11 main functions in order to support and maintain life: absorption, digestion, respiration, biosynthesis, excretion, egestion, secretion, movement, irritably, homeostasis, and reproduction.

they assemble membranes that control the flow of molecules, energy, and information into and out of the cell

they make RNA that transcribe sections of DNA to translate into amino acids to form polymers that fold to perform functions

they build trails for proteins to walk on to arrive where needed

they metabolize organic molecules to release energy and to synthesize other biomolecules

some of them use sunlight or chemical energy sources for biosynthesis

they gather information about their environment and make decisions to accomplish goals

they influence the environment which selects successful evolutionary changes

they provide structure for multicellular organisms

they provide specialized functions in tissues in organs of multicellular organisms

some of them sacrifice themselves for the sake of the multicellular organism

Back to top

Bacteria interact with algae, fungi, plants, and animals. Photosynthetic bacteria bury atmospheric carbon dioxide and release oxygen and formed symbiotic relationships with fungi in lichen which helped transition life to land. Some eukaryote organelles evolved through endosymbiosis with bacteria cells. Animals cannot digest food without bacteria.

Back to top

Back to top

new41

The last eukaryote common ancestor LECA was a heterotroph or consumer, not a producer. How were its descendants able to evolve into so many diverse kingdoms? What were the advantages of such diversification? nuclei, mitochondria, …    and algae inherited photosynthesis from cyanobacteria by endosymbiosis

What roles do attributes like adhesion, communication, specialization, and sacrifice play in the evolution of multicellularity? How did they evolve? Did they emerge by repurposing particular molecules, structures, and metabolic processes? What were the impacts of division of labor in cyanobacteria and the great oxygenation event? How and why do cells make decisions to balance cooperation and competition for the benefit of the organism? How did multicellularity arise in each eukaryote kingdom?

Back to top

Back to top

Back to top

Back to top

Taxonomy is an attempt to categorize organisms that actually evolved from a universal common ancestor along nearly continuously varying paths. In 2015, the seven kingdoms of life classification model included two prokaryote kingdoms and five eukaryote kingdoms that evolved from a eukaryote common ancestor that formed from prokaryotes through endosymbiosis.

Bacteria: The simplest and most primitive form of life. These small unicellular organisms are prokaryotic, meaning they don’t have a nucleus to store their DNA. Some bacteria including the all important cyanobacteria form filaments with two types of cells, an important step toward multicellularity. Bacteria have formed important relationships with fungi, algae, plants, and animals, sometimes mutual, sometimes not so mutual.

In human terms (https://www.center4research.org/bacteria-good-bad-ugly/):

Bacteria are everywhere, including your entire body. The bacteria in our body weighs as much as our brain: three pounds! Bacteria can be harmful, but some species of bacteria are needed to keep us healthy. The bacteria on our skin, in our airways, and in our digestive system are the first line of defense against foreign “invaders” (pathogens) that can cause infection and other problems.

Bacteria also act as “tuning forks” for our body’s immune system, making sure it’s pitched just right. The immune system shouldn’t be too sensitive or too sluggish: it needs to respond quickly to an infection but it shouldn’t over-react. (If it does over-react and attacks the body itself, the result is an autoimmune disease, such as rheumatoid arthritis, lupus, or MS). Each person has a personalized collection of bacteria, called the microbiome. We acquire our first bacteria while being born, and every day our environment exposes us to more. Some of these bacteria will take up residence inside the body and help develop a robust immune system.

Archaea: This is the second prokaryotic kingdom, but its members have genes and metabolic processes that are more related to eukaryotes than bacteria. Archaea utilize a widely diverse range of energy sources that no other kingdoms use, allowing them to live in environments uninhabitable by others.

Protozoa: The most primitive eukaryotic kingdom in phylogenetic history. Protozoa include a diverse range of unicellular organisms and are thought to be the evolutionary origin of all other eukaryotic kingdoms. Examples of protozoa include amoeba, euglena, and paramecium.  Cellular slime molds are particularly interesting because of their ability to behave like a multicellular organisms using important features like cell signaling.

Chromista: This kingdom of eukaryotes acquired photosynthesis independently of the organisms in the plant kingdom which includes red and green algae. Chromists contain different types of photosynthetic organelles and are found in water rather than on land. Examples of chromists are kelp and diatoms. single-celled and multicellular eukaryotic species that share similar features in their photosynthetic organelles (plastids). It includes all protists whose plastids contain chlorophyll c, such as some algae, diatoms, oomycetes, and protozoans.

Fungi: This kingdom of eukaryotes includes unicellular and multicellular fungi. Unlike the other eukaryotic kingdoms, multicellularity evolved many times from unicellular ancestors and some of the unicellular organisms evolved from multicellular ancestors.

Fungi and animals share a common eukaryote common ancestor. This kingdom is more biochemically and genetically similar to Kingdom Animalia than Plantae. Fungi have a cell wall like plants, but it is made of a different carbohydrate. Yeasts are single celled examples and mushrooms are the aboveground fruiting bodies of multicellular fungi that are otherwise hidden underground. Fungi play a vital role with relationships with bacteria, algae, and plants, without which life on land may never have gained a foothold. Networks of fungal hyphae filaments connect plants and span vast distances.

One possible scenario: Fungi survived and thrived on the decomposing matter that blanketed Earth following the mass extinction of the the asteroid impact 66 mya. Mammals (and avian dinosaurs) being warm blooded are more resistant to fungi and survived and thrived when fungi inherited to the Earth. In fact, warm blooded organisms may have evolved to increase resistance to fungal pathogens. Hibernating bats are susceptible to fungal disease.

Animalia: This eukaryotic kingdom contains some of the most complex organisms on our planet. All animals are multicellular, mobile, and do not have a cell wall. Kingdom Animalia includes mammals, reptiles, and birds, but also simple organisms such as sponges, sea anemones, worms. Animals have numerous vital relationships with each other and with members of other kingdoms.

Plantae: This eukaryotic kingdom includes all land plants and red and green algae. All land plants are multicellular, but some groups of algae are not. This is the only photosynthetic kingdom found on land as well as in water. As previously mentioned, they have important relationships with other kingdoms. For one thing, plant cells cannot fix atmospheric nitrogen or nutrient phosphorus without the help of other organisms, a quirk of the fact that land plants evolved from algae that evolved by endosymbiosis of a single celled cyanobacteria that could not fix carbon and nitrogen in the same cell.

Brain evolution: Where did our brains come from?

Brains have their origin billions of years ago in simple single-celled organisms.

3.4 BYA bacteria began to develop ion channels, membrane proteins that control the flow of ions, paving the way for nerve conduction.

~2 BYA Eukaryote cells developed the ability to make electrical signals when they swam.

600 MYA sponges and comb jellies developed further features seen in modern nervous systems. Sponges organized colonies with proteins used in modern synapses. Comb jellies evolved on of the first neural networks.

550 MYA flatworms developed primitive bilaterally symmetric nerve cords and lights sensors (eyes) which led to early fishes with complex brains inside a protected spinal-cord-like structure.

350 MYA amphibians developed a complex forebrain.

200 MYA mammals entered the scene, further evolving the forebrain.

200,000 years ago, modern humans appeared with every more complex brains and reasoning abilities.

Back to top

new