Predict the evolution of the variety of fish in the African Rift Valley lake compared to other lakes with similar microhabitats.
Understand how macroevolution is not goal-oriented.
Darwin believed that macroevolution occurs gradually.
Natural selection can only bring about change in each generation.
The model suggests that speciation occurs after populations become isolated.
The proponents of the gradualistic model often show the history of groups of organisms by drawing a diagram.
An ancestral species has given rise to two separate species, represented by a slow change in color.
There are equilibriummodels.
New species evolve from a series of small changes over time under the gradualistic model.
A lot of transitional forms are brought about by this process.
New species evolve from a series of rapid changes after a period of little or no change.
Different species would result from this process.
After studying the fossil record, some paleontologists tell us that species can appear suddenly and then remain essentially unchanged until they either undergo extinction or evolve in response to changes in the environment.
The assembly of species in the fossil record can be explained by periods of equilibrium, interrupted by periods of rapid speciation or change, according to this model.
A strong argument can be made that it is not necessary to choose between the two models of evolution, and that both could help us understand the fossil record.
Some fossil species may fit one model and some may not.
A species can be kept in equilibrium in a stable environment.
A species may be able to adapt slowly if the environment changes slowly.
When we consider that geologic time is measured in millions of years, the sudden appearance of a new species in the fossil record could be thousands of years old.
Alterations in body shapes and organs can be brought about by genes.
Scientists are trying to understand how evolution could have produced so many animals.
They are trying to figure out how genetic changes brought about the differences.
Since the time of Darwin, it has been suggested that the answer must involve the processes that shape development.
In 1917, D'Arcy Thompson asked us to imagine an ancestor in which all parts are developing at a particular rate.
A change in gene expression can stop a process or prolong it.
If the growth of limb bones were stopped early, the result would be shorter limbs, and if it was extended, the result would be longer limbs.
If the whole period of growth were extended, a larger animal would result, accounting for why some species of horses are so large today.
Using the modern techniques of cloning and manipulating Page 311 genes, investigators have discovered genes whose differences in expression can bring about changes in body shapes and organs.
The results suggest that the genes must be from a common ancestor that lived more than 600 mya, and that all animals share the same control switches for development.
The animal kingdom has many different types of eyes, which were thought to require their own set of genes.
Humans and other animals have the same camera-type eye with a single lens.
Humans are not related to flies or squids, so it would seem that all three types of animals have different eye genes.
This is not the case.
The Tbx5 is thought to have triggered the transcription of only one gene.
Changes in the genes regulated by Tbx5 and other transcription factors could have led to the evolution of limb formation.
Body shape can be affected by subtle changes in gene control.
This could explain the variation in plant and animal shape and form.
There is a question of timing.
A dramatic change in shape can be caused by changing the timing of Page 312 genes.
The vertebral column is an example of repeating segments.
Changes in the number of segments can affect the overall shape.
The expression of these genes can be shifted to explain why insects have just six legs.
There are two types of stickleback fish in North American lakes.
The stickleback is protected from being eaten by large predators in the open waters of a lake.
On the lake bottom, long pelvic spines are a disadvantage, because dragonfly larvae grab young sticklebacks and feed on them.
During the evolution of other animals, hind limbs have been reduced.
Legless lizards have evolved many times.
The stickleback study shows how natural selection can lead to changes in the body in a short time.
Our DNA base sequence is very similar to that of Chimpanzees, mice, and all other animals.
There are around 20,000 genes in the human genome.
Based on this knowledge and the work just described, investigators no longer expect to find new genes to account for the evolution of humans.
It is a random process that creates variation in genes.
Evolution cannot occur without variation.
Natural selection is not random.
Natural selection acts on the variation that is present, in a way that favors the survival of beneficial traits in a particular environment.
This shouldn't be seen as evidence that evolution works towards an end goal.
Variations from generation to generation are shaped by evolution.
There is a complicated array of external forces that affect this process.
evolution isn't directed toward any particular end.
The evolution of the horse showed an increase in overall size, toe reduction, and a change in tooth size and shape.
The evolution of the horse is complicated by the presence of many different lineages that went extinct, and thus were not on the path to the modern horse.
If the goal of the modern horse was to have a single branch on this tree with intermediate fossils leading from the ancestors to the horse, we would see a single branch on this tree.
Every dot is a group.
The horse was adapted to its environment.
The members of a population with an advantage are able to have more children.
Natural selection is not goal-directed.
The animals had a wooded habitat, ate leaves and fruit, and were about the size of a dog.
About 35 mya was where the first adaptive radiation of horses occurred.
Grasses were evolving as the weather became dry.
Increased size and longer legs would have allowed greater speed to escape, as eating grass requires tougher teeth.
The horse family was diversified by 10.
Some species were large forest browsers and others were small forest browsers.
Some species had only one strong toe.
Page 313 features that were adaptive for living on an open plain include large size, long legs, hoofed feet, and strong teeth.
The other groups of horses became extinct because of complex reasons.
Humans have corralled modern horses for various purposes, and this makes it difficult to realize that the horse's characteristics are adapted for living in a grassland environment.
There are genes that influence macroevolution.
Prezygotic isolation occurs prior to fertilization, while postzygotic isolation occurs after fertilization.
The genes of the parents can't be passed on to the next generation.
Over time, genetic changes can accumulate through microevolution.
Various natural selection mechanisms favor certain genes.
The ancestral species and the new species are no longer compatible.
Two populations of the same salamander species are unable to reproduce when they come in contact with each other because of the evolution of a series of salamander subspecies on either side of the Central Valley of California.
When populations of the same species become specialized on a particular food item in the same geographic area, it's rare, but it can happen.
The arrow cichlid, a new species, differed from the midas cichlid in a single lake because it specialized in feeding in open water.
As populations become specialized in newly available microhabitats, ecological release provides an opportunity for new species to originate.
The rise of mammals after the extinction of dinosaurs is one example of adaptive radiation events.
Allopatric speciation can lead to adaptive radiation.
Birds and bats are examples of convergent evolution.
In environments that are similar to geographically isolated ones, an adaptive radiation and convergent evolution can produce similar types of cells.
Lake Tanganyika and Lake Malawi have similar cichlids as a result of convergent evolution.
Evolution of new species and higher levels of classification is called macroevolution.
The fossil record shows a view of life over millions of years.
The hypothesis that species evolve gradually is being challenged by another.
The fossil record could show periods of stasis interrupted by spurts of change.
With gradual change, transitional fossils would be expected.
It is most likely that species have evolved from a combination of gradualism and punctuated equilibrium.
The process would have been affected by environmental factors.
Both models can be seen in the fossil record, but rapid change can occur by differential expression of regulatory genes.
The genes that control the development of a pelvic girdle are the same ones that control the other genes.
Dramatic changes in shape can be caused by changing the timing of gene expression.
The evolutionary history of a species shows that macroevolution is not goal-directed.
The life we see about us is indicative of how we adapt to certain environments.
In the future, such adaptions will change.
Pick the best answer for the question.
A biological species is different from other species.
Male moths use chemical signals to find females.
This is an example of gamete isolation.
An egg cannot be fertilized by sperm.
Use the phrases genetic changes, geographic barrier, species 1, species 2, and species 3 to complete the diagram.
Isolation speciation is the creation of new species due to geographic barriers.
The finches are adapted to eating different foods.
This is the result of a flow of genes.
Speciation requires reproductive isolation.
All of these are correct.
You want to use a definition of a species in a study.
A member of the audience stated at a recent school board meeting that there wasn't enough evidence to support how various species have arisen.
He or she thinks that students should be given alternative ideas to the theory of evolution due to the lack of evidence.
The modern horse is an example of the scientific lines of evidence used to support the process of speciation.
Genetics can cause a population to undergo speciation over time.
Different species can be prevented from being able to reproduce successfully.