Compendium Review Untit 4 Topic 2

Table of Contents

Human Evolution

• Origin of Life
• Biological Evolution
• Classification of Humans
• Evolution of Hominids
• Evolution of Humans

Global Ecology and Human Interferences

• The Nature of Ecosystems
• Energy Flow
• Global Biogeochemical Cycles

Human Population, Planetary Resources, and Conservation

• Human Population Growth
• Human Use of Resources and Pollution
• Biodiversity
• Working Toward a Sustainable Society

Human Evolution

Origin of Life

One fundamental principle of biology states "all living things are made of cells and every cell comes from a preexisting cell" It is believed that the sun and planets were formed over 10 billion years from dust particles. The first atmosphere was formed from gases escaping volcanos. As Earth cooled, the vapors condensed to liquid water and rained in enormous quantities making the oceans. The rain washed N2 and CO2 into the oceans. Energy was in the form of volcanoes, meteorites, radioactive isotopes, lightning and ultraviolet radiation. With all this energy these gases may have reacted together to form organic compounds such as nucleotides and amino acids. These small molecules would join to form macromolecules. There are two hypothesis one is the RNA-first hypothesis and the second is the protein-first hypothesis that result in the formation of microspheres. A true cell can reproduce and today this is done by DNA and cell division

Biological Evolution

The first true cells were prokaryotic and lacking a nucleus. Later eukaryotic cells with a nucleus evolved, then multicellularity. Biological evolution is the process by which a species changes over time. Two aspects are decent from a common ancestor and adaptation to the environment. Adaptation is why there is diversity of life and different types of living things. Natural selection is a mechanism for adaptation. Charles Darwin first formulated the theory of evolution. The evidence used to convince him of common descent were

1. Fossils- actual remains of species that lived at least 10,000 years ago
2. Biogeographical- study of the distribution of plants and animals in different places throughout the world
3. Anatomical- common descent offers explanation for anatomical similarities between different organisms

Evolution is a scientific theory based on evidence collected in a number of different fields. The natural selection process has three critical elements

1. Variation- individuals of a species have varying characteristics that can be passed on to generations
2. Competition for limited resources- limited resources results in unequal reproduction among members of a population
3. Adaptation-members with advantageous traits capture more resources and are liklier to reproduce and pass those traits on.

Classification of Humans

The binomial name gives the genus and species. Organisms in the same domain have only general characteristics in common, if in the same genus they have specific characteristics in common. Today major decisions regarding the history of life are being made using DNA, rRNA and protein sequencing data.

Humans are primates in the anthropoids group. Primates are adapted for tree living and have mobile limbs, grasping hands, flattened face, binocular vision, complex brain, and a reduced reproduction rate. Hands and feet have 5 digits each some with opposable thumbs.

Evolution of Hominids

By studying the characteristics of a group of organisms biologists construct and evolutionary tree that becomes a working hypothesis of their past history. Hominid refers to our branch of the evolutionary tree. When two lines of descent (lineage) first diverge from a common ancestor, the genes and the lineages are nearly identical. Paleontologists use anatomical features when they determine if a fossil is hominid such as bipedal posture, the shape of the face and brain size.

Evolution of Humans

Fossils are put in the genus Homo is the brain size is at least 600cm cubed, the jaw and teeth resemble those of humans, and tool use is evident. Homo habilis, dated approx 1.9 mya may have been the ones to start culture, possibly started by hunting cooperatively. Culture emcompasses human behavior and products and depends on the capacity to speak and transmit knowledge. H. erectus was the first hominid to use fire and fashion more advanced tools for cutting and scraping.

The majority of researchers believe H. sapians evolved from H. erectus. Multiregional continuity hypothesis believes H. sapians evolved in several different locations (Asia, Africa, and Europe). Out-of-Africa hypothisis believes H.sapians evolved from H. erectus, but only in Africa and then migrated. Since humans have evolved they have been widely distributed about the globe. Phenotypic and genotypic variations are noticable between populations, today this is know as ethnicities.

Global Ecology and Human Interferences

The Nature of Ecosystems

The biosphere is where organisms are found on Earth (fromt the atmosphere to the oceans). An ecosystem is where organisms interact among themselves and with the physical and chemical environment. Distinctive types of terrestrial ecosystems are known as biomes. Temperature and rainfall define these biomes containing communities of organisms that have adapted to the regional climate. There is the tropical rainforest, savanna, temperate grasslands, forests, deserts, taiga, tundra. Aquatice ecosystems are divided by fresh water(standing or running) and salt water (marine)

Abiotic components of an ecosystem are non living and biotic are living and are classified by their food source.

1. Autotrophs- require only inorganic nutrients and produce organic nutrients for themselve and others
2. Heterotrophs- need organic nutrients. They are consumers. Made up of herbivores, carnivores and omnivores.

A niche is the role of an organism in an ecosystem- how it gets food, how it eats that food, and how it interacts with other populations in the same community.

Energy Flow

A trophic level is composed of all organisms that feed at a particular link in a food chain .Only about 10% of the energy of one trophic level is available to the next trophic level. This flow of energy between trophic levels is shown as an ecological pyramid.

Global Biogeochemical Cycles

All organisms require a variety of organic and/or inorganic nutrients. The pathways by which chemicals circulate through ecosystems involve both living and nonliving components and are known as biogeochemical cycles. These can be gaseous or sedimentary. A reservoir is a source unavailable to producers. An exchange pool is a source where organisms take chemicals, that have moved there through the food chain. Human activities remove chemicals from the resovoirs and exchange pools and make them available to the community. This upsets the normal balance of nutrients for producers in the environment and causes pollution.

1. Water Cycle- humans interfere by withdrawing water from aquifers, clearing vegetation to build roads that increases runoff and interfere with natural purification and instead add pollutants to water
2. Carbon Cycle-by burning fossil fuels more carbon is added to the air, and also forests are being destroyed
3. Nitrogen Cycle- humans double the fixation rate by producing fertilizers from N2
4. Phosphorus Cycle-overenrichment of waterways is due to mining, runoff and livestock wastes

Human Population, Planetary Resources, and Conservation

Human Population Growth

The present population is about 7 billion people, and undergoing exponential growth. Growth rate is determined by the difference between the number of people born per year and the number who die per year. Biotic potential is the maximum growth rate under ideal conditions. Carrying capacity is the maximum population that the environment can support for an indefinite period. Today there are two groups the more developed countries- show modest population growth and have a good standard of living and then the less developed countries- exhibit dramatic population growth and generally live in poverty.

There are three age groups in populations: Pre-reproductive, reproductive, and postreproductive. The LCDs are experiencing growth because they have more women entering reproductive years then leaving them.

Human Use of Resources and Pollution

Humans have basic needs and a resource is anything from the biotic or abiotic environment that can help meet these needs. Nonrenewable resources are limited in supply (land, fossil fuels, minerals). Renewable resources can be naturally replenished (solar energy, harvesting plants and animals for food). Pollution is any alteration of the environment in an undesirable way. (Desertification, deforestation, dams, aquifiers, subsidence, saltwater intrusion)

Biodiversity

This is the variety of life on earth which is described in terms of number of different species. Today, the number of extinctions predicted to occur in the near future is unparralleled in Earth's history. Factors that contribute to this include

1. habitat loss
2. alien species
3. pollution- acid deposition, global warming, ozone depletion, synthetic organic chemicals
4. overexploitation
5. disease

Many individual species contribute beneficial services to human beings and the value that needs to be placed on biodiversity.

1. Medicinal value-many prescriptions originally derived from living organisms
2. Agricultural value- crops modified to be high producers originally from wild plants, flowering plants pollinated by wild animals
3. Consumptive use value

Indirect value

1. Waste disposal
2. Provision of Freshwater
3. Prevention of Soil Erosion
4. Biogeochemical cycles
5. Regulation of Climate
6. Ecotourism

Working Toward a Sustainable Society

A sustainable society would always be able to provide the same amount of goods and services for future generations the same as it does in the present. To achieve this resources must be preserved. A natural ecosystem makes use of only renewable solar energy, and materials cycle through back to producer (coral reefs).

Works Cited

Mader, Sylvia. Human Biology 10th ed

Frolich Powerpoint

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