Compendium Review Unit 4- Topic 2

Compendium Review Unit 4- Human Populations: Reproduction and Ecology- Topic 2- Human Landscapes


Chapter 22- Human Evolution

22.1- Origin of Life
22.2- Biological Evolution
22.3- Classification of Humans
22.4- Evolution of Hominids
22.5- Evolution of Humans

22.1- Origin of Life
A chemical evolution produced the first cells. The sun and the planets were formed probably over a 10 billion year period. 4.6 billion years ago the solar system was in place. The Earth’s atmosphere was very hot at first and the water was existing only as a gas which formed thick, dense clouds. But once the Earth cooled down the water vapor condensed to liquid water and rain began to fall. So much rain fell that the oceans were formed. There were a lot if sources for energy then such as volcanoes, meteorites and lightning. The RNA- first hypothesis consists of only the macromolecule RNA was needed to progress toward formation of the first cells. RNA can be a substrate and an enzyme during RNA processing. Because DNA is a double helix and is more stable it rather than RNA became permanent genetic material. Cells have lipid-protein membranes. Protocell’s carry on metabolism but not reproduce. A heterotroph is an organism that takes in preformed food.

22.2- Biological Evolution
The process of which a species changes through time is known as biological evolution. 2 important aspects of this are descent from a common ancestor and adaptation to the environment. If adapted it is able to survive and reproduce in the environment. Fossils are the actual remains of species that lived 10,000 years ago and more. These are traces that any past life existed, such as trails, footprints, burrows and preserved droppings. Weathering and erosion of rocks produces an accumulation of particles that vary in size and nature are call sediment. Sedimentation has been going on since the Earth was formed. This can take place on land or in bodies of water. For fossils to be dated sediment becomes a layer in a sequence of layers. The older layer is above and younger than the one directly below. The fossil record, history of life recorded by fossils, is evidence that evolution has occurred. The first signs of life in this record are unicellular prokaryotes, then unicellular eukaryotes and then multicellular eukaryotes. Fossils that have characteristics of 2 different groups are transitional fossils. Whales had terrestrial ancestors. The earliest mammals were shrew size creatures in fossil beds about 200 million years old.
The study of the distribution of plants and animals in different places around the world is known as biogeography. Homologous structures are structures that are anatomically similar because they are inherited from a common ancestor. Now structures that are not constructed similarly and do not have a common ancestry, but do serve the same function are known as analogous structures. Vestigial structures inherit their anatomy from their ancestors, they are anatomical features that are fully developed in one group but reduced in other similar groups. Biochemical evidence shows that all living organisms use the same biochemical molecules. They use the same DNA and 20 amino acids in their proteins. Humans share a lot of genes with simpler organisms. A small protein in the electron transport chain that plays an important role is known as cytochrome c, this shows that humans differ from monkeys by 2 amino acids. Charles Darwin believed in natural selection, that is species become adapted to their environment. There are three elements for the natural selection process, variation- physical variation can be passed on, individuals vary in physical characteristics, competition for limited resources- numbers in generation stay about the same due to food competition and resources, adaptation- the environment selects for better adapted traits.

22.3- Classification of Humans
The binomial name of an organism is what gives its genus and species. Those in the same domain have only general characteristics in common, while those in the same genus have specific characteristics in common. Major decisions regarding history of life come down to DNA/rRNA/protein sequencing table. Mitochondrial DNA helps decide timing of recent evolutionary events because it changes frequently. Primates are adapted to living in trees. They have mobile limbs, grasping hands, large complex brains, binocular vision, flattened face, and reduced reproductive rates. 2 suborders make up the order of Primates, lemurs, tarsiers and lorises make up the prosimians and monkeys, apes and humans make up anthropoids. The hands and feet of primates have 5 digits each and the opposable thumb helps for grasping and a powerful grip.

22.4- Evolution of Hominids
Evolutionary trees are working hypothesis of past history for characteristics of a group organisms in which biologists have studied. The belief that humans evolved from apes is one that Darwin believes and is a misconception. Humans and apes are believed to have a common ape like ancestor. For 7 million years humans and apes have been separately evolving from a common ancestor. Hominids refer to our branch of the evolutionary tree. If a fossil is in the hominid line of descent that means it is closer to us than to the African apes. If 2 lines of descent called a lineage diverge from a common ancestor then the genes and proteins of the 2 lineages are nearly identical. The protein changes and RNA changes are because with each lineage genetic changes accumulate. Some features of hominids are walking on two feet, shape of face and brain size. The human jaw is shorter than an apes jaw. A brain of a chimpanzee is 400 cm3 in size while a human brain is that of 1,300 cm3. Fossils from when apes and human lineages split have been found. The oldest fossil is from 7 MYA called Sahelanthropus tchadensis. It was found in central Africa. It was a skull. The orrorin tugenensis is from 6 MYA and also found in Africa.

22.5- Evolution of Humans
Fossils are assigned to the genus Homo if the brain size is 600 cm3 or greater, if the jaw and teeth resemble those of humans and if tool use is evident. Homo habilis may be ancestors to modern humans dated between 2.0 and 1.9 MYA. Culture depends on capacity to speak and transmit knowledge. Homo erectus was the first hominid to use fire and fashioned more advanced tools. Scientists accept that homo sapiens evolved from H. erectus. The out-of-Africa hypothesis proposes H. sapiens evolved from H. erectus but only in Africa and then they migrated to Europe and Asia. Many scientists support this hypothesis. There is a Neandertal skeleton from 200,000 years before present, they get their name from Neander Valley, Germany. The out-of-Africa hypothesis says they were supplanted by modern humans. They were culturally advanced, they lived in caves. The oldest fossils to be designated as homo sapiens are known as cro-magnons. These might have been the first to have a language. They painted drawings of animals on the cave walls in Spain and France.

Chapter 23- Global Ecology and Human Interferences

23.1- The Nature of Ecosystems
23.2- Energy Flow
23.3- Global Biogeochemical Cycles

23.1- The Nature of Ecosystems
Organisms found on Earth are in the biosphere, this is one giant ecosystem. An ecosystem is a place where organisms interact with themselves and with the physical and chemical environment. Biomes are distinctive terrestrial ecosystems, such as temperature and rainfall define the biomes containing communities of organisms adapted to regional climate. Aquatic ecosystems are divided into those composed of freshwater and those composed of salt water. The ocean being a marine ecosystem covers 70% of the Earth’s surface. Standing water and fresh water make up 2 freshwater ecosystems. Abiotic components of an ecosystem are the nonliving components. Biotic are living things that can be categorized according to the food source. These are autotrophs, and some heterotrophs. Autotrophs require inorganic nutrients and outside energy sources for production of organic nutrients for own use and others of the community. These are producers because they produce food. Heterotrophs need a source of organic nutrients. These are consumers because they consume food. Herbivores eat plants and algae. Carnivores eat other animals. Omnivores eat both. Detritus feeders eat decomposing particles of organic matter. Niche is the role of an organism in an ecosystem. Energy flow and chemical cycling characterizes every ecosystem.

23.2- Energy Flow
Shortness of food chains can be attributed to loss of energy between trophic levels. An ecological pyramid shows the flow of energy with large losses between successive trophic levels. Biomass is the number of organisms multiplied by the weight of organic matter within one organism, pyramids of this eliminate size as a factor.

23.3- Global Biogeochemical Cycles
Organisms require a variety of organic and/or inorganic nutrients. Biogeochemical cycles are pathways that chemicals circulate through involving living and nonliving components. The water cycle shows transfer rate of water between components of an ecosystem. Evaporation is the sun rays causing freshwater to evaporate from seawater, leaving salts behind. The vaporized water rises, condenses and then falls as precipitation. Also evaporates from plants and land. Because of gravity freshwater eventually returns to the see. If water doesn’t run off it can sink or percolate into the ground saturating the earth. Top saturation zone is called the water table. Aquifers are rock layers that contain water, releasing it to wells or springs. Interference from humans includes withdrawing water from aquifers, clearing vegetation from land and natural processes which purify water. Groundwater mining refer to withdrawals from aquifers exceeding the possibility of recharge.
The carbon cycle consists of carbon dioxide in the atmosphere, where the exchange pool is. Terrestrial and aquatic ecosystems exchange carbon dioxide with the atmosphere. Respiration and combustion add carbon dioxide to the atmosphere. It is recycled to plants. Greenhouse gases allow solar radiation to pass through but hinder the escape of heat back into space. The rise in the Earth’s temperature referred to as global warming is because of the greenhouse effect. If the temperature continues to rise more water will evaporate, making more clouds which could increase this more. Coastal areas could disappear as water continues to rise.
78% of atmosphere is nitrogen gas, plants cannot make use of this. Production of nitrates during the nitrogen cycle is called nitrification. This can occur by Nitrogen gas turns into nitrate in the atmosphere when cosmic radiation provides the high energy needed. Denitrification is the process which nitrate converts back to nitrogen gas. Human activities alter transfer rates in this cycle by producing fertilizers. When fertilizers run off into lakes and rivers the algae overgrows. Acid deposition is when nitrogen oxides and sulfur dioxide enter the atmosphere from fuel of burning fossils.
The phosphorus cycle has three components known as reservoir, exchange pool and biotic community. Bacteria converts nitrogen gas to ammonium. Cultural eutrophication is the overenrichment of waterways which the runoff of fertilizer can cause. Biological magnification is the process of substances becoming more concentrated in organisms in higher trophic levels. Many species are almost to the point of extinction because of humans polluting the seas and exploiting their resources.