Early Forms of Life on Earth (Lesson 8) - PDF

Lesson 8 Early Forms of Life  Evidence of Early Life The Earth was formed for about 4.5 billion years ago while the first life form emerged 3.7 billion years ago. The Timeline of Life Notable events: 3.5 bya: photosynthetic organisms 1.85 bya: eukaryotes 541-mya: Cambrian explo...

Lesson 8 Early Forms of Life  Evidence of Early Life The Earth was formed for about 4.5 billion years ago while the first life form emerged 3.7 billion years ago. The Timeline of Life Notable events: 3.5 bya: photosynthetic organisms 1.85 bya: eukaryotes 541-mya: Cambrian explosion Some early life forms still exist, or descendants are still seen today. PRECAMBRIAN Cyanobacteria Cyanobacteria or the blue green algae are prokaryotic organisms They are photosynthetic. Cyanobacteria are prokaryotic organisms that lack nuclei in their cells. As a consequence, most prokaryotes are unicellular in nature. Cyanobacteria bloom What do you think happened during the Cambrian explosion that led to the increase in species of organisms on Earth? Some early life forms still exist, or descendants are still seen today. CAMBRIAN EXPLOSION GYMNOSPERM ❖ Gymnosperms were dominant in the Mesozoic Era (about 252.2 million to 66 million years ago), during which time some of the modern families originated ❖ Although since the Cretaceous Period (about 145 million to 66 million years ago) gymnosperms have been gradually displaced by the more recently evolved angiosperms, ❖ They are still successful in many parts of the world and occupy large areas of Earth’s surface. Red Algae ❖ The first multicellular organisms are thought to be red algae that appeared 1.2 billion years ago. ❖ The earliest microfossils of red algae were collected in northern Arctic Canada and were dated 1.2 billion years ago. ❖ The red algae are unique as it started sexual reproduction in organisms. Red algae Trilobites ❖ Trilobites were the dominant species during the Cambrian period. These organisms are extinct forms of arthropods, animals having hard shells and jointed legs. ❖ Trilobites were relatives of modern lobsters and horseshoe crabs. This first animal on Earth had three segmented top-plated bodies. Trilobite illustration Trilobites ❖ They curl up like balls to protect themselves in seas with predators. Trilobites have several varieties. They usually range from an inch to more than 2 feet in length. ❖ These organisms have been the most successful prehistoric animals. More than 17,000 species are known to have existed that survived for 300 million years. Trilobite illustration Anomalocaris ❖ One of the most dominant animals of the Cambrian Period is the giant Anomalocaris. ❖ They trap prey using their two claws lined with hooks located in front of their mouths and eyes. ❖ These are gigantic creatures that reach up to six feet in length. A replica of the Anomalocaris. Anomalocaris ❖ Anomalocaris is a free-swimming animal that moves like a dolphin. They feed on trilobites and other arthropods and worms. ❖ Anomalocaris is considered as the largest and most fearsome predator of the Cambrian Period. A replica of the Anomalocaris. FERNS ❖ For approximately 450 million years another leap on the evolution of land plants is the widespread evolution of spores which is also present in today’s fern species. ❖ Spores are unicellular structures that are mobile and are capable of reproducing new plant individuals. Fern frond with spores Land Animals ❖ Primitive Earth did not have an ozone layer that protects the organisms against the effects of UV radiation from sunlight. ❖ With the oxygen-rich atmosphere, an ozone layer was formed that made land a safer ecosystem to tread. ❖ The first large animals to walk the Earth is probably in the form of a walking fish which still lived in water. Acanthostega Land Animals ❖ One of the earliest known tetrapods is the Acanthostega. It is an extinct group of tetrapods which is considered as one of the oldest organisms with distinct recognizable limbs. Four legged creature and the ❖ This emerged during the late origin of reptile, amphibian and mammals Devonian period which is 365 million years ago. ❖ Scientists are telling that the Acanthostega is the missing link between the lobe-finned fishes and tetrapods. Acanthostega TIMELINE OF EVOLUTION - MEMORIZE THIS! 4 EONS OF EVOLUTION ❖ Hadean Eon - Period of Young Earth and earliest possible appearance of LIFE ❖ Archean Eon - Rock/Soil Formation, rising of photosynthetic bacteria and rising of oxygen in the atmosphere ❖ Proterozoic Eon - Evolution of eukaryotic and multicellular organisms and beginning of animal evolution ❖ Phanerozoic Eon - Period of well-displayed life  3 Era of Phanerozoic Eon 1. Palaeozoic Era - major diversification of plants and animals 2. Mesozoic Era - Jurassic Period/great plants and animals 3. Cenozoic Era - Evolution of primates, increase in diversity of organisms and at the same period; the extinction of PRIMITIVE plants and animals ICE AGE  DIFFERENT PERIODS Mesozoic Era - Jurassic Period/great plants and animals EXTINCTION OF DINOSAURS  DIFFERENT PERIODS Cenozoic Era - Evolution of primates, increase in diversity of organisms and at the same period; the extinction of PRIMITIVE plants and animals We are in this period ICE AGE  YOUR REFERENCE  The Earth was formed about 4.5 billion years ago 1 while the first life form emerged 3.7 billion years ago. The Cambrian explosion is an event that 2 happened around 541 million years ago in the Cambrian period. The Cambrian explosion resulted in the 3 divergence of most modern animals and plants.  Bibliography Aleksandr Ivanovich Oparin. 2003.The Origin of Life. Massachusetts: Courier Corporation. Matthew S. Dodd, Dominic Papineau, Tor Grenne, John F. Slack, Martin Rittner, Franco Pirajno, Jonathan O’Neil & Crispin T. S. Little. 2017. Evidence for early life in Earth’s oldest hydrothermal vent precipitates. Nature: 543, pages 60–64. Larry L. Hench. 2001. Science, Faith, and Ethics.Singapore: World Scientific. Lisa A. Shiel. 2009. The Evolution Conspiracy, Vol 1: Exposing Life’s Inexplicable Origins and the Cult of Darwin.Texas: Jacobsville Books. Sandra Alters. 2000.Biology: Understanding Life. Massachusetts: Jones & Bartlett Learning. Shri Hemant Roy. 2005.Comprehensive MCQs in Biology.New Delhi: Golden Bells. Rakesh Kumar Rastogi. 2007. Concepts of Biology XII. New Delhi: Rastogi Publications.  Photo Credits Slide 11: Acanthostega_model.jpg by Dr. Gunter Benchly, is licensed under CC BY-SA 3.0 via Wikimedia Commons. Peter J. Russell, Paul E Hertz, and Beverly McMillan. 2016. Biology: The Dynamic Science, Boston: Cengage Learning. Jason P. Schrum, Ting F. Zhu, and Jack W. Szostak. 2010. The Origins of Cellular Life. Cold Spring Harbor Perspectives Biology.