Because plant cells have chloroplasts and can do photosynthesis, why do they also need mitochondria?

What are the distinguishing characteristics of the free living members of sarcodina?

murzikaleks [220]

The distinguishing characteristics of the free living members of sarcodina are:

1. These are pseudopods (function in locomotion) which makes it the extentions of protoplasm.

2. These have both a clear ectoplasm and a granualated endoplasm.

3. These have nucleus both food vacuoles and contractile vacuoles.

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3 years ago

PLEASEEE HELLPPP PLEASEE SOMEONE ANSWERR THISSS PLEASEEEEEEEEEE

vichka [17]

1) Natural Selection- General speaking, something must cause differential reproduction and then better suited individuals will survive over time.

- Detailed Explanation -

Natural selection is the process in which individuals whom are better suited to their environment will have an increase in fitness. It occurs over multiple generations and can take a very long period of time to occur.

For natural selection to occur, the following must be true:

1. There must be variation in traits (every individual can't be identical)

2. There must be differential reproduction (some individuals are more likely to reproduce than others)

3. Traits are passed on from generation to generation

Thus, the first step in natural selection is that something must cause differential reproduction. This could be the introduction of a predator, a disease, a random mutation that is detrimental, a change in resource availability such as a drought, and so forth.

This image shows how a genetic mutation is unfavorable and is selected against, but the same process holds for a gene that is unfavorable during any scenario.

This event causes some individuals to survive and reproduce and some to be less successful. For example, a predator is introduced and it hunts and kills mostly individuals with shorter legs that run slowly. Or the environment undergoes a long drought and individuals in the species who have a gene that helps them perspire (sweat) less are more successful.

Over multiple generations, the genetic composition of the species changes. Maybe within six generations the predator has completely wiped out individuals with shorter legs. Maybe within two generations the drought completely eliminates individuals with a gene that results in excess perspiration. The amount of time will vary.

2) Mutation - A change in the genetic structure of an organism.

Explanation:

Usually, a mutation has to be expressed as some macro-functional characteristic although some may be hidden in internal systems.

3) Genetic Drift- Genetic drift is the change in the frequency of an existing allele in a population due to random sampling of organisms.

Explanation:

The effect of genetic drift is larger when there are few copies of an allele, whereas when there are many copies the effect is smaller.

Genetic drift describes random fluctuations in the number of gene variants in a population. Once it begins, genetic drift will continue until the involved allele is either lost by a population or until it is the only allele present in a population at a particular locus. Both possibilities reduce the genetic diversity of a population.

Genetic drift can cause a new population to be genetically distinct from its original population, which has led to the hypothesis that it plays a role in the evolution of new species.

4) Gene Flow- Gene flow is a concept in population genetics to refer to the movement of genes or alleles between interbreeding populations of a particular species.

Explanation:

Gene flow is an important mechanism for transferring genetic diversity among populations. Migrants into and out of a population may result in a change in allele frequencies, thus changing the distribution of genetic diversity within the populations. High rates of gene flow can reduce the genetic differentiation between the two groups, increasing homogeneity.

It is thought that gene flow constrains speciation by combining the gene pools of the groups and thus, prevents the development of differences in genetic variations that would have led to full speciation. It is expected to be lower in species that have low dispersal or mobility, occur in fragmented habitats, there is a long distance between populations, and smaller population sizes.

It includes different kinds of events, such as pollen being blown to a new destination or people moving to new cities or countries. However, there are certain factors that serve as barriers to gene flow. Some of the factors affecting the rate of gene flow include physical barriers, geological events and geographical barriers.

5)Non Random mating- The nonrandom mating is a selective pattern.

Explanation:

The nonrandom pattern of mating is an assortative pattern of sexual reproduction. During the reproduction, similar phenotypes are selected for mating. It is a random process. It is also known as positive assortative mating.

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3 years ago

In the trp operon, attenuation occurs through the recognition of two tryptophan codons in the leader sequence. what would happen

Sati [7]

If a lot of tryptophan is present, the operon will be repressed.
Under intermediate amounts of tryptophan, the change to stop codons would cause the ribosome to stall and therefore would mimic as if there were no tryptophan present.
If no tryptophan present, the operon would be maximally expressed.

a - True. The ribosome would always be stalled in the leader sequence - so this wouldn't matter. However, the operon would still be transcribed because the repressor would be active (remember Trp operon is controlled both by attenuation and repression). True as long as there's not much tryptophan to activate the repressor!
b- True - With no tryptophan the repressor isn't engaged and the ribosome is stalled in the leader sequence.
c- Matters about how much tryptophan is available. So True if there's lots of tryptophan available.
d- I would choose this one as all of the above could be true depending on the levels of tryptophan.

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3 years ago

how does secondary succession differ from primary succession? it begins on bare rock or land, it begins where no plants have gro

Nitella [24]

in georgia or in the crib

4 0

3 years ago

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Which choice best describes the relationship between biodiversity and invasive species?

german

Answer:

b. As invasive species increase, it causes biodiversity to decrease

Explanation:

Invasive species refers to those species of organisms that are foreign (non-native) to a particular environment or habitat with the tendency to outgrow and outcompete the native species in that habitat. Due to their fast reproductive and growth rate, they tend to diminish the population of native species by using up the available nutrients.

Biodiversity is the richness of organism species on Earth. When invasive species increase in a particular habitat or ecosystem, they cause the biodiversity in that habitat to decrease because they tend to take charge and dominate, causing harm to every other species. Hence, As INVASIVE SPECIES INCREASE, it causes BIODIVERSITY TO DECREASE

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3 years ago