Unit 7 Lesson 2: Natural Selection Over Time Flashcards
natural selection
a process by which individuals that are better adapted to an environment survive better and reproduce more often
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heritable trait
a trait that can be passed down genetically from parent to offspring
There are four major parts of natural selection:
Genetic variation
There are naturally occurring variations in a population because of meiosis, which can create new allele combinations. Variation can also be introduced by mutations, or changes, in DNA. These mutations can sometimes be helpful to the organisms by creating alleles of genes that give the organism a survival or reproductive advantage.
Correlation between natural selcetion and hertiable traits
In natural selection, heritable traits, or traits that are inherited from parent to offspring, that help organisms survive and reproduce become more common in a population over each generation.
Because parents pass on some of their traits to their offspring, the next generation will have more of the traits of the
reproducing individuals.
There are four major parts of natural selection:
Overproduction and Competition-
There are more offspring born than the environment can support. This produces competition for limited resources in the ecosystem.
There are four major parts of natural selection:
Selection
a process in which certain indivduals outperfrom others in terms of survial or reproduction due to some factor
There are four major parts of natural selection:
Inheritance and Adaption
Traits are passed from parent to offspring. Some of these traits are beneficial and help the individual survive better and reproduce more often in the environment. These traits are known as adaptations, and they tend to accumulate in a population due to the environment and natural selection.
adaptation
a trait that gives the individual a survival advantage in a certain environment
At first there are more mice with white fur than the mice with darker fur. How did this change
The mice with the white fur are easier to see and are eaten by the fox. In the next generation, there are more mice with darker fur.
The mice with the white fur are easier to see and are eaten by the fox. In the next generation, there are more mice with darker fur. This is known as melanistic gene frequency,
the prevalence of a gene that codes for dark color
A second example of natural selection at work can be observed in the same place where Darwin first studied animals on the Galápagos Islands. Two scientists, Rosemary and Peter Grant studied the finches on the islands for a long period of time. The Grants learned a lot about the finches’ beak morphology, or beak shape.
During times of drought on the island, the finches with larger beaks were able to eat the seeds available and survived. The following year, there were more larger-beaked birds to reproduce, resulting in more offspring with larger beaks. The offspring inherited the genes for larger beaks from their parents, and in turn, these larger beaks gave these offspring an advantage since they were better able to utilize the food available on the island after the drought. Natural selection had caused an evolution in beak size that can be observed on the graph.
Until recently, scientists believed that natural selection was entirely dependent on genetics. New research shows that there is more than just the makeup of genes in natural selection. epigenetics
The word epigenetics refers to changes in an organism that can’t be explained by the sequence of its DNA.
Until recently, scientists believed that natural selection was entirely dependent on genetics. New research shows that there is more than just the makeup of genes in natural selection. Elaboarte
For example, certain genes within a sequence of DNA may be turned on or off in response to environmental changes, such as changes to diet or exposure to pollution. Epigenetic changes can occur more quickly than genetic changes that take place through random mutations.
Natural selection is often summed up as “Survival of the Fittest.” Does that mean that natural selection means that the strongest creatures survive over time? Explain.
Not necessarily. Natural selection is better described as the survival of the genes that are passed down to the next generation. For different species, different qualities help them pass down genes. For example, while for some species, more muscle mass would help an organism to pass down their genes, for others, more muscle mass would take energy away from more important functions, so more muscular organisms would be more likely to die of hunger before reproducing.
You hear the radio saying that due to our overuse of antibiotics, bacteria “have learned” how to become immune to these antibiotics. But bacteria don’t have brains and aren’t capable of learning. Based on what you’ve learned about natural selection, explain why bacteria are actually becoming immune to antibiotics.
Certain bacteria develop mutations that cause them to be immune to antibiotics. These are the bacteria that aren’t killed by antibiotics, so they are the ones that can reproduce. Many of these mutant bacteria are able to pass their immunity mutations to their offspring. Over time, the predominant bacteria are the ones that are immune to antibiotics.
Why would correlating melanistic gene expression to pollution be important?
Pollution can darken buildings and trees, making dark-colored organisms more difficult to see. Because of this, the pollution creates an environment in which darker-colored organisms have a survival advantage. Since this relationship correlates an inheritable trait to survival based on the environment, it creates a scenario to test natural selection.
Why do you think charts, tables, and graphs would be especially important in the study of natural selection?
Since natural selection can only be studied over a number of generations, gathering and tabulating data is essential. Charts, tables, and graphs let scientists observe patterns. For example, scientists see changes in populations and how they may correlate to changes in the environment. In addition, adding to a graph over time lets any upward or downward trends become apparent, which helps scientists to know what correlations may be causal.
One important factor in the sudden success of melanistic moths is not discussed in the video. What do you think that factor is?
Melanistic moths became more successful because they were not as easy to see. The reason this drove their success is that being harder to see made them harder to eat. Predators saw the pale colored moths more easily, so they were more likely to be eaten before they could produce offspring.
Why would it be harder to identify an inherited trait that is a behavior instead of a physical trait?
Behaviors can arise through environment, learning, or heredity, and could be a combination of all those factors. The capacity to learn to read, for instance, may be something that is passed on through the genes (it is probably impossible to teach a goldfish, for instance, how to do it), but the ability is one that must be learned. This makes it difficult to be certain if an individual’s behavior is hereditary. Some morphological traits, such as size, are influenced by the environment: a finch that starved as a hatchling will seldom grow up to be as large as one who has always received adequate nutrition. For the most part, though, physical traits are more easily seen as being passed from parent to offspring.
What are other reasons besides natural selection that might cause the finches to show a fear response?
The fear response might be passed on as a learned behavior from parents who learned it from their own parents, even though they themselves have never known predation.
