Biology: Evolution

Question 1

Evolution

Answer 1

The change in the genetic makeup of a population with time. Explained by the constant propagation of new variations in the genes of a species, some of which impart an adaptive advantage.

Question 2

Fossil Record

Answer 2

Fossils are the most direct evidence of evolutionary change. They represent the preserved remains of an organism. Fossils are generally found in sedimentary rocks.

Question 3

Actual Remains

Answer 3

Type of fossil that includes teeth, bones, etc., in rock, tar pits, ice, and amber (the fossil resin of trees).

Question 4

Petrification

Answer 4

It’s the process in which minerals replace the cells of an organism.

Question 5

Imprints

Answer 5

Impressions left by an organism. (footprints)

Question 6

Molds

Answer 6

Form hollow spaces in rocks, as the organisms within decay.

Question 7

Casts

Answer 7

Formed by minerals deposited in molds.

Question 8

Trilobite

Answer 8

A primitive crustacean (relative of the lobster), which was a dominant form of the early Palezoic era.

Question 9

Dinosaurs

Answer 9

Ancient animals related to both reptiles and birds. Various forms lived on land, in the air, and in water. They were a dominant form of the Mesozoic era.

Question 10

Eohippus

Answer 10

The dawn horse. A primitive horse the size of a fox with four toes and short teeth with pointed cusps for feeding on soft leaves. Fossil evidence indicates gradual change to the modern horse, which has one toe (hoof) and two vestigial toes as side splints, flat teeth with ridges for grinding grain, and tough prairie grass, and long legs for running.

Question 11

The Woolly Mammoth

Answer 11

A hairy elephant found in the Siberian ice.

Question 12

Saber-tooth Tigers

Answer 12

Have been preserved in asphalt tar pits.

Question 13

Amber

Answer 13

Fossilized resin that oozed from threes. Can preserve insects.

Question 14

Archaeopteryx

Answer 14

The link between reptiles (it has teeth and scales) and birds (it also has feathers).

Question 15

Homologous Structures

Answer 15

Have the same basic anatomical features and evolutionary origins. They demonstrate similar evolutionary patterns with late divergence of form due to differences in exposure to evolutionary forces. Examples include the wings of a bat, the flipper or a whale, the forelegs of horses, and the arms of humans.

Question 16

Analogous Structures

Answer 16

Have similar functions but may have different evolutionary origins and entirely different patterns of development. The wings of a fly (membranous) and the wings of a bird (bony and covered with feathers) are analogous structures. Analogous organs demonstrate a superficial resemblance that cannot be used as a basis for classification.

Question 17

Comparative Embryology

Answer 17

The stages of development of the embryo resemble the stages in an organism’s evolutionary history. The human embryo passes through the stages that demonstrate common ancestry. The two-layer gastrula is similar to the structure of the hydra, a cnidarian. The three-layer gastrula is similar in structure to the flatworm. Gill slits in the embryo indicate a common ancestry with fish.

Question 18

Comparative Biochemistry (Physiology)

Answer 18

Most organisms demonstrate the same basic needs and metabolic processes. They require the same nutrients and contain similar cellular organelles and energy storage forms (ATP).

For example, respiratory systems are very similar in most organisms. The similarity of the enzymes involved in these processes suggests that all organisms must contain some DNA sequences in common. The more recently organisms shared a common ancestor, the greater the similarity of their chemical constituents and genetic info.

Question 19

Divergence

Answer 19

The more time that has elapsed since the divergence of two species, the more different their biochemical characteristics.

Question 20

Vestigial Structures

Answer 20

Have no known current function, but may have had some ancestral function.

Question 21

Appendix

Answer 21

In humans, the appendix is small and useless. In herbivores, it assists in the digestion of cellulose.

Question 22

Tail

Answer 22

In humans, the tail is reduced to a few useless bones (coccyx at the base of the spine.

Question 23

Splints

Answer 23

Splints on legs of horses are the vestigial remains of the two side toes of Eohippus.

Question 24

Phython Legs

Answer 24

Python “legs” are reduced to useless bones embedded int he sides of the adult. The whale has similar hind-limb bones.

Question 25

Geographic Barriers

Answer 25

Species multiplication is generally accompanied by migration to lessen intraspecific competition. Separation of a widely distributed population by emerging geographic barriers increases the odds of genetic adaptations on either side of the barrier. Each population may evolve specific adaptations to the environment in which it lives, in addition to the accumulation of neutral (random, nonadaptive) changes. These adaptations will remain unique to the population in which they evolve., provided that interbreeding is prevented by the barrier.

In time, genetic differences will reach a point where interbreeding becomes impossible between the populations and reproductive isolation will be maintained even if the barrier was removed.

Question 26

Marsupials

Answer 26

A lineage of pouched mammals (marsupials) paralleling the development of placantal mammals developed on the Australian side of a large water barrier. The geographic barrier protected the pouched mammals from competition and hybridization with modern placental mammals. This barrier resulted in the development of uniquely Australian marsupials, such as kangaroos and pouched wolves, as well as other Australian plants and animals such as the eucalyptus tree and duckbilled platypus.

Question 27

Darwin’s Finches

Answer 27

Over a comparatively short period of time, a single species on finch underwent adaptive radiation to form 13 different species of finches. Slight variations in the beak, for example, favored ground or tree feeding. Such adaptations minimalized the competition among the birds, enabling each emerging species to become firmly entrenched in its environmental niche.

Question 28

Lamarckian Evolution

Answer 28

Proposed by Jean-Baptise Lamarck. Discredited. Held that new organs of changes in existing ones arose because of the needs of an organism. The amount of change was thought to be based on the use or disuse of the organ. This was based upon a fallacious understanding of genetics. Any useful characteristic acquired in one generation was thought to be transmitted to the next.

Modern genetics disproved theories of acquired characteristics. Only changes in the DNA of the sex cells can be inherited. Changes acquired during an individual’s life are changes in the characteristics and organization of somatic cells. These are not inherited.

Question 29

Overpopulation

Answer 29

More offspring are produced than can survive. Thus, there is insufficient food, air, light, and space to support the entire population.

Question 30

Variations

Answer 30

Offspring naturally show differences in their characteristics compared to their parents’. Darwin did not know the source of these differences. Hugo De Vries suggested mutations as the cause. Some mutations are beneficial, but mostly harmful.

Question 31

Competition (Struggle for Survival)

Answer 31

The developing population must compete for the necessities of life. Many young must die, and the number of adults in the population generally remains constant from generation to generation.

Question 32

Natural Selection

Answer 32

Some organisms in a species have variations that give them advantages over other members of the species. In the struggle for existence, these organisms have adaptations that increase odds of survival. “Survival of the fittest”.

Question 33

Inheritance of the Variations

Answer 33

The ones that survive live to adulthood, reproduce their own kind, and thus transmit these favorable variations/adaptations to their offspring.

Question 34

Evolution of New Species

Answer 34

Over many generations, the favorable changes are accumulated to the point where there’s so many changes of the gene pool that a new species has evolved.

Question 35

Gene Pool

Answer 35

The gene pool of a population is the sum total of all the alleles for any given trait in the population.

Question 36

Gene Frequency

Answer 36

The decimal fraction representing the presence of an allele for all members of a population that have this particular gene locus.

Question 37

The Hardy-Weinberg Principle

Answer 37

Evolution can be viewed as a result of changing gene frequencies in a population. When the gene frequencies are not changing, the gene pool is stable, no evolution. This is only true in ideal situations.

• The population is large.
• No mutations affect the gene pool.
• Mating between individuals in population is random.
• No net migration of individuals in and out of population.
• The genes in the population are all equally successful at reproducing.

Under these conditions, a certain equilibrium will exist among all the genes in the gene pool, which is described as the Hardy-Weinberg Equation.

Question 38

The Hardy-Weinberg Equation

Answer 38

For a gene locus with only two alleles, T and t, p = frequency of allele T and q= frequency of allele t. By definition, for a given gene locus, p + q = 1, since the combined frequencies of the alleles must total 100%. So (p+q)^2 = (1)^2 and

p^2 + 2pq + q^2 = 1

p^2 = frequency of TT
2pq = frequency of Tt
q^2 = frequency of tt

ONLY applicable under conditions of Hardy-Weinberg Principle.

Question 39

Assortive Mating

Answer 39

If mates are not randomly chosen but rather selected such as phenotype and proximity, the relative genotype ratios will be affected and will depart from the predictions of the Hardy-Weinberg equilibrium.

Question 40

Genetic Drift

Answer 40

Refers to changes in the composition of gene pool due to chance. Tends to be more pronounced in small populations or new populations, where it is sometimes called the founder effect.

Question 41

Gene Flow

Answer 41

Migration of individuals between population will result in loss or gain of genes, thus changing composition of gene pool.

Question 42

Deme

Answer 42

Small local population. Like all the beavers along a specific portion of a river form a deme.

May be many demes belonging to a species. Members of a deme resemble one another more closely then they resemble memebers in other demes.

Question 43

Adaptive Radiation

Answer 43

The emergence of a number of lineages from a single ancestral species. A single species may diverge into a # of distinct species; the differences between them are those adaptive to a distinct lifestyle, or niche.

Question 44

Phylogeny

Answer 44

Evolutionary history among the species alive today. Can be visualized as a branching tree, where the common ancestor is found at the trunk.

Question 45

Convergent Evolution

Answer 45

Different species evolving in similar ways when in similar environments.

Question 46

The Heterotroph Hypothesis

Answer 46

The first forms of life lacked the ability to synthesize their own nutrients; they required preformed molecules. These “organisms” were heterotrophs, which depended on outside sources for food. The seas contained simple inorganic and organic compounds like salts, methane, ammonia, hydrogen and water. Energy was present in heat, electricity, solar radiation, cosmic rays, and radioactivity.

Presence of these building blocks and energy may have led to the synthesis of simple organic molecules like sugar, amino acid, purines, and pyrimidines. These molecules dissolved in the “primordial soup”, and after many years, the simple monomeric molecules combined to form a supply of macromolecules.

Question 47

Evidence of Organic Synthesis

Answer 47

In 1953, Stanley L. Miller set out to demonstrate that the application of ultraviolet radiation, heat, or a combination of these to a mixture of methane, hydrogen, ammonia, and water could result in formation of complex organic compounds. Miller set up an apparatus in which the four gases were continuously circulated past electrical discharged from tungsten electrodes.

After circulating the gases for one week, Miller analyzed the liquid int he apparatus and found that an amazing variety of organic compounds, including urea, hydrogen cyanide, acetic acid, and lactic acid had been synthesized.

Question 48

Formation of Primitive Cells

Answer 48

Colloidal protein molecules tend to clump together to form coacervate droplets (a cluster of colloidal molecules surrounded by a shell of water). These droplets tend to absorb and incorporate substances from the surrounding environment. In addition,t he droplets tend to possess a definite internal structure. It is highly likely that such droplets developed on early earth. Although these droplets weren’t living, they possessed some properties associated with living organisms.

Most of these systems were unstable; however, a few systems may have arisen that were stable enough to survive. A small percentage of droplets possessing favorable characteristics may have eventually developed into the first primitive cells. These first cells probably possessed nucleic acid polymers and became capable of reproduction.

Question 49

Development of Autotrophs

Answer 49

The primitive heterotrophs slowly evolved complex biochemical pathways, which enabled them to sue a wider variety of nutrients. They evolved anaerobic respiratory processes to convert nutrients into energy. However, these organisms required nutrients at a faster rate than they were bring synthesized. Life would have ceased to exist if autotrophic nutrition had not developed. The pioneer autotrophs developed primitive photosynthetic pathways, capturing solar energy and using it to synthesize carbohydrates from CO2 and H2O.

Question 50

Development of Aerobic Respiration

Answer 50

The primitive autotrophs fixed CO2 during the synthesis of carbohydrates and released oxygen as a waste product. The addition of oxygen to the air converted the atmosphere from a reducing to an oxidizing one. Some molecular oxygen was converted to ozone, which functions int he atmosphere to block high-energy radiation. This way, living organisms destroyed conditions that made their development possible. Once molecular oxygen became a major component of Earth’s atmosphere, both heterotrophs and autotrophs evolved biochemical pathways of aerobic respiration. Now equilibrium exists between oxygen-producing and oxygen-consuming organisms.

Question 51

General Categoris of Living Organism

Answer 51

Autotrophic Anaerobes include chemosynthetic bacteria.

Autotrophic Aerobes include green plants and photoplankton.

Heterotrophic Anaerobes include yeasts.

Heterotophic Aerobes include amoebas, earthworms, and humans.