Chapter 22Evolution is a scientific theory, ideas that scientists have found to be all encompassing because they are based on evidence collected.
Evolution begins with the origin of life. Biology states that all living things are made of cells and every cell comes from a preexisting cell. Non living chemicals could be how the first cells came to be created by a chemical evolution.
Earth was probably formed over a 10 billion year period. Earth’s atmosphere is much different today then when it was first formed. The primitive atmosphere was more than likely formed by gases escaping from volcanoes so therefore had little if any free oxygen.
The oceans of the world were produced by enormous amounts of rain over hundreds of millions of years.
A protocell which can not reproduce but can carry on metabolism could have come into existence. Since it could not take in molecules in the ocean for food, it more than likely was an organism that took in preformed food and being a fermenter and not requiring free oxygen because primitive Earth had no free oxygen.
Scientists were trying to figure out how cells had both RNA and DNA. By doing many hypotheses they found out that RNA formed from enzymes and then they could use RNA as a template to form DNA.
In today’s cells, DNA replicates before cell division occurs because true cells reproduce. The replication process is carried out by enzymatic proteins.
The first true cells were the simplest of life forms and lacked a nucleus, later cells which have a nuclei evolved. All of these organisms are alive today.
Almost all living organisms use the same basic biochemical molecules, including DNA, ATP, and many enzymes. Humans share a large number of genes with much simpler organisms. Life’s vast diversity came about by only a slight difference in the regulation of genes.
Biological evolution: is the process by which a species changes through time.
Two aspects to this type of evolution: descent from a common ancestor and adapt to the environment and adapt to different environments and be able to survive and reproduce in this environment.
A mechanism for adaptation called natural selection. Members of a species vary in physical characteristics. There are limited resources that mean there is competition for it which results in unequal reproduction among members of a population.
Adaptation to changes in the environment and selects for better adapted traits natural section accounts for the great diversity life. Every organism adapt differently to their own way of life.
Fossils which are the actual remains of species that lived on Earth at least 10,000 to billions of years ago are the best evidence for evolution.
Fossils can be: trails, footprints, burrows, worm casts, preserved droppings, pieces of bones, impressions of plants, insects in tree amber, Most fossils are found embedded in rock. Many things have been learned about primitive life by studying fossils including history of life, climates and environments.
The origin of mammals is well documented by studying fossils. The earliest true mammals are about 200 million years old.
The study of distribution of plants and animals in different places throughout the world is Biogeography. There are different mix of plants and animals in separate continents, islands and seas. Some animal types may not be in some continents because they evolved somewhere else and had no way of reaching other parts even though the environment might be suited for them. Many unique species make their home in the islands of the world but are not found anywhere else in the world. The reason for this is they migrated to that island and then evolved into different species on that island. Many times evolution is influenced by the mix of plants and animals in a particular continent.
The anatomical similarities among organisms can be explained that the basic plan belonged to a common ancestor and the plan was adapted as each group continued along its own evolutionary path. Some are similar because they are inherited from a common ancestor, however in contrast some have structures that serve the same function but they are not constructed the same nor do they share a common ancestry.
During adaptation a species becomes suited to its environment, this process is natural selection. Variation, competition for limited resources such as food and adaptation are the elements of this process. This accounts for the diversity of life in the different environments and why the adaptations are varied.
Humans are primates, meaning they have mobile limbs, grasping hands, a flattened face, binocular vision, a large complex brain and a reduced reproductive rate. Humans are most closely related to monkeys and apes because monkeys and apes have certain characteristics similar to us.
The first modern humans were Neandertals and Cro-Magnons and later Homo habilis which may be the ancestor to modern human, the study of fossils date the early homo between 2.0 and 1.9 MYA and the jaw and teeth resemble those of humans. It is very unlikely that human evolution produced the same result in different places. Therefore human populations have evolved separately for along time with genetic differences.
Since the beginning of human evolution just like with other species, human beings have been widely distributed about the globe. Today we say that people have different ethnicities. One hypothesized theory is that human variations evolved to adapt to a certain environment, like the difference between humans skin color. However other differences among ethnic groups such as hair texture and shape of lips cannot be explained as adaptation to the environment. These features may have been fixed in different ethnic populations simply by genetics.
Chapter 23
Ecosystem: is a place where organisms interact with themselves and the environment physically and chemically.
Organisms are found on planet earth from the atmosphere to the depths of the oceans and everything in between is known as the biosphere. The entire biosphere is one giant ecosystem.
The different ecosystems
Temperature and rainfall define the biomes, which contain communities of organisms adapted to the regional climate
Tropical rain forest, which occurs at the equator, is dominated by large evergreen, broad leaved trees.
Savanna is tropical grassland that supports many types of grazing animals.
Temperate grasslands receive less rainfall than temperate forest and more water than deserts which lack trees.
Taiga is a very cold northern coniferous forest and the tundra which borders the North Pole, is also very cold, long winters and short growing seasons.
Aquatic ecosystems are those composed of freshwater and those composed of salt water.
The role of an organism in an ecosystem like how it gets its food, what it eats and how it interacts with other populations in the same community is a niche.
Non living components of the ecosystem are abiotic components. Biotic components are living things that are categorized by their food source.
Some species are autotrophs and are called producers because they produce food. Other species are called heterotrophs and they need a source of organic nutrients. They consume food so are therefore consumers.
Herbivores: animals that graze directly on plants or algae
Carnivores: animals that feed on other animals
Omnivores: animals that feed both on plants and animals
Detritus feeders: organisms that feed on detritus (decomposing particles of organic matter)
All species play an important role in the food chain, therefore are important to the ecosystem.
Global biogeochemical cycles: pathways by which chemicals circulate through ecosystems involve both living and nonliving components. All organisms require a variety of organic and/or inorganic nutrients. Global biogeochemical cycle can be gaseous or sedimentary.
The water cycle—evaporation from the ocean, precipitation to ocean, precipitation over land, transportation from plants, evaporation from soil, freshwater runoff, aquifer
The carbon cycle---plants take up carbon dioxide from the air and incorporate carbon into nutrients, when organisms respire carbon is returned to the atmosphere therefore carbon recycles to plants by the atmosphere, carbon dioxide from the air combines with water to produce HCO3, the amount of HCO3 in the water is in equilibrium with the amount of carbon dioxide in the air, living and dead organisms contain organic carbon and serve as reservoirs for the carbon cycle, plant and animal remains were transformed into fossil fuels, carbon dioxide is released into the atmosphere.
Greenhouse gases are contributing significantly to an overall rise in the Earth’s ambient temperature, a phenomenon referred to by scientists as global warming. This effect could bring about other changes.
Chapter 24
Growth rate is determined by considering the different between the number of persons born per year and the number who die per year.
The carrying capacity is the maximum population that the environment can support for an indefinite period.
The more development countries (MDC) typified by countries in north America and Europe, population growth is modest and people enjoy a good standard of living.
The less development countries (LDCS) typified by some countries in Asia, Africa, and Latin America population growth is dramatic and the majority of people live in poverty.
People can help out ecological by driving energy efficient car, living in a smaller house, owning fewer possessions, eating vegetables as opposed to meat.
Living right on the coast can be bad because it leads to beach erosion and loss of habitat for marine organisms and loss of a buffer zone for storms. About 70% of the world’s beaches are eroding.
In water poor areas of the world, people might not have clean drinking water or impure. Food comes from three activities: growing crops, raised animals and fishing the seas.
Genetic engineering produces transgenic plants with new and different traits. Researchers hope to produce crops that tolerate salt drought and cold.
Modern society runs on various types of energy. Some are nonrenewable such as fossil fuels and global climate change. Others are renewable: hydropower,geothermal energy, wind power, energy and the solar hydrogen revolution and photovoltaic solar cell.
Life on earth is biodiversity which means the number of species on earth. We are now in a biodiversity eristic because of extinction. Why is biodiversity so important? Different species perform useful services for human beings and contribute greatly to the value we should place on biodiversity.
A sustainable society will always be able to provide the same amount of goods and services for future generations as it does at present.
We are quick to realize that population growth in the LDCs creates an environmental burden, we also need to consider excessive resource consumption of the MDCs also stresses the environment.
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