Is there any organism that is born with all the nutrients and resources needed for their entire lifetime?

Is there any organism that is born with all the nutrients and resources needed for their entire lifetime?

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I understand that adult mayflies have no mouth, but they do take in oxygen through openings in their exoskeleton.

Is there any organism that does not need to ingest any type of nutrition and does not need to take in something for cellular respiration?

You may need to clarify your question: As written, this would be the biological equivalent of a perpetual motion machine. No such organism could reproduce without either violating the first and second laws of thermodynamics, or ultimately evaporating into nothingness as it divides.

No, I think this fails even on simply definitional terms. That is, Life is (sometimes) defined as meeting certain criteria, such exhibiting growth, metabolism, and response to stimuli. Those will all require intake of some external substance at some point.

To get even more pedantic, all cells have a cell membrane, which is selectively permeable to certain molecules. Every organism will thus passively let in some substances from the environment, and thereby failing your criteria.

Luna moth , so I expect there are other moths.

I would point that maybe there is an organism that can pass enough nutrients to 1 generation to survive and reproduce, but not continuously generation after generation. Search in this camp, you may find something.

Red wolves are lean canids, often with black-tipped bushy tails. Their coats are mostly a brown or buff color, with some black along their backs. There is sometimes a reddish tint to the fur on their muzzle, behind their ears, and on the backs of their legs. At a glance, a red wolf may look somewhat like the domestic German shepherd.

The red wolf is between the size of a gray wolf and a coyote. They are about four feet long and stand about 26 inches at the shoulder. Red wolves weigh anywhere between 45 and 80 pounds, with males averaging about 60 pounds and females about 50 pounds.

Historically the red wolf ranged from southeastern Texas to central Pennsylvania. Today the only place red wolves can be found in the wild is in eastern North Carolina's Albemarle Peninsula. Equally at home in forests, swamps, and coastal prairies, red wolves can thrive in a wide range of habitats.

Red wolves are carnivores, though their diet can vary depending on what prey is available. Mostly they hunt smaller mammals like raccoons, rabbits, and rodents, along with white-tailed deer. Within their territory, red wolves will travel up to 20 miles in search of prey.

Red wolves mate for life, and each pack is formed around the breeding pair. Usually red wolves form a group of five to eight, composed of the breeding male and female and their offspring from different years. The pack is a very close family unit. Older offspring will help the breeding male and female raise their younger siblings, and will also attend the den. Within one to three years, the younger wolves will leave the pack in search of their own mates and territory.

Each pack has its own home range, which the wolves will hunt in and defend from other canids. Red wolves are fiercely territorial creatures and will even fight other wolves if needed. Red wolves breed once a year, from January through March. Anywhere from one to nine pups are born roughly nine weeks later in April or May. After about 10 days, the pups' eyes open. For several weeks after this period, the other members of the pack keep a close eye on the pups, keeping them within the den until they mature.

The dens themselves are well hidden near stream banks, downed logs, sand knolls, or even drain pipes and culverts. The adult pack members will range and return with food for the pups until they are strong enough. In the wild, red wolves typically live five to six years, and as long as 14 years in captivity.

Smaller and ruddier in color than their gray wolf cousins, the red wolf is one of the most endangered canids in the world. Though red wolves once ranged across the southeastern United States, years of hunting and habitat loss had driven the species to the brink of extinction by 1970. As part of an ambitious captive-breeding program, the U.S Fish & Wildlife Service captured the 14 remaining red wolves they could find in the wild. These wolves are the ancestors of the 75 to 100 animals that now live in North Carolina, the first animal to be successfully reintroduced after being declared extinct in the wild.

Within their ecosystem, the wolves play a valuable role in keeping numbers of prey like deer in check. In turn the smaller prey populations are less likely to balloon out of control and consume all available nutrients in their habitat. Additionally, though no studies have conducted to quantify this, the wolves’ preference for nuisance species, like nutria and raccoons, helps to reduce damage to crops and other human activities.

Though the red wolf has come a long way, there are many threats to the species in the long term. While they are a distinct species, their interactions with coyotes pose a serious risk of hybridization. Coyotes have moved into the habitat range formerly occupied by the red wolf and now compete with the reintroduced wolves for resources. Though the smaller coyotes do not pose a direct challenge to red wolf territory, any potential offspring between coyotes and red wolves endangers the red wolf’s long-term viability as a unique species. Thankfully management actions by wildlife managers, such as sterilizing territorial coyotes, are limiting hybridizations events, and giving red wolves the advantage and opportunity to increase their numbers.

Human interactions also pose a risk to the red wolf. Their entire habitat in the Albemarle Peninsula rests just three feet above sea level, and as a result climate change poses a serious threat. Though shy by nature and unlikely to confront humans, further development and habitat fragmentation increases the chance of conflict between the two species. Some of these interactions may be accidents caused by auto collisions, but some confrontations are more malicious.

In the past few years there has been a rash of red wolf killings. In less than a month in late 2013, six red wolves were found shot, and the attacks continue. The presence of tampered radio tracking collars and the ongoing attacks outside of hunting season suggests evidence tampering and foul play. In a population of less than a hundred animals, the impact of these attacks is immense.

Red wolves communicate through body language, scent marking, and a series of vocalizations. These include the characteristic howl, along with a series of barks, growls, and yaps. The red wolf’s howl sounds somewhat similar to a coyote’s, but is often lower pitched and lasts longer.

Finding Challenges Basic Reproductive Biology Beliefs

Researchers say that the theory that female mammals are born with a fixed supply of eggs stems from studies that showed females develop a finite number of egg-producing follicles in their ovaries during fetal life, as opposed to males who continue to generate sperm-producing cells throughout their lives.

"Although this dogma has persisted for more than 50 years, the present study provides evidence that challenges the validity of this belief, which represents one of the most basic underpinnings of reproductive biology," write researcher Joshua Johnson of Harvard Medical School and colleagues.

Rather than having a fixed supply of egg-producing follicles, the study shows that female mice have a reserve supply of cells that replenish the follicle pool during adolescence as damaged follicles die.

In the study, researchers carefully measured follicle numbers at birth and then tracked their subsequent loss in female mice. They found that adolescent mice had about 2,500-5,000 healthy follicles but the number of dying follicles increased rapidly to up to 1,200 per ovary after adolescence.

Dying follicles degenerate or disappear within a few days, which means that the total number of healthy follicles should have dropped rapidly during this time period. Instead the study showed that in female mice the ovaries contain a population of cells that are required to maintain overall number of follicles for adult life.

Researchers found that the number of healthy follicles actually decreased relatively slowly despite this rapid loss of follicles. That finding shows that healthy egg-producing follicles must be produced somewhere in young mouse ovaries.

To test this theory, researchers treated the young mice with a chemical that kills egg cells and instead found that the mice still produced viable eggs in adulthood.

Researchers say the results show that a reserve of stem cells that form the building blocks for reproductive cells must exist in female mice as they do in male mammals. But more research is needed to determine how they function and what causes them to decline after adolescence.


Evolutionary adaptation, or simply adaptation, is the adjustment of organisms to their environment in order to improve their chances at survival in that environment.

Biology, Ecology, Conservation


Some creatures, such as this leafy sea dragon fish (Phycodurus eques) have evolved adaptations that allow them to blend in with their environment (in this case, seaweed) to avoid the attention of hungry predators.

In evolutionary theory, adaptation is the biological mechanism by which organisms adjust to new environments or to changes in their current environment. Although scientists discussed adaptation prior to the 1800s, it was not until then that Charles Darwin and Alfred Russel Wallace developed the theory of natural selection.

Wallace believed that the evolution of organisms was connected in some way with adaptation of organisms to changing environmental conditions. In developing the theory of evolution by natural selection, Wallace and Darwin both went beyond simple adaptation by explaining how organisms adapt and evolve. The idea of natural selection is that traits that can be passed down allow organisms to adapt to the environment better than other organisms of the same species. This enables better survival and reproduction compared with other members of the species, leading to evolution.

Organisms can adapt to an environment in different ways. They can adapt biologically, meaning they alter body functions. An example of biological adaptation can be seen in the bodies of people living at high altitudes, such as Tibet. Tibetans thrive at altitudes where oxygen levels are up to 40 percent lower than at sea level. Breathing air that thin would cause most people to get sick, but Tibetans&rsquo bodies have evolved changes in their body chemistry. Most people can survive at high altitudes for a short time because their bodies raise their levels of hemoglobin, a protein that transports oxygen in the blood. However, continuously high levels of hemoglobin are dangerous, so increased hemoglobin levels are not a good solution to high-altitude survival in the long term. Tibetans seemed to have evolved genetic mutations that allow them to use oxygen far more efficently without the need for extra hemoglobin.

Organisms can also exhibit behavioral adaptation. One example of behavioral adaptation is how emperor penguins in Antarctica crowd together to share their warmth in the middle of winter.

Scientists who studied adaptation prior to the development of evolutionary theory included Georges Louis Leclerc Comte de Buffon. He was a French mathematician who believed that organisms changed over time by adapting to the environments of their geographical locations. Another French thinker, Jean Baptiste Lamarck, proposed that animals could adapt, pass on their adaptations to their offspring, and therefore evolve. The example he gave stated the ancestors of giraffes might have adapted to a shortage of food from short trees by stretching their necks to reach higher branches. In Lamarck&rsquos thinking, the offspring of a giraffe that stretched its neck would then inherit a slightly longer neck. Lamarck theorized that behaviors aquired in a giraffe's lifetime would affect its offspring. However, it was Darwin&rsquos concept of natural selection, wherein favorable traits like a long neck in giraffes suvived not because of aquired skills, but because only giraffes that had long enough necks to feed themselves survived long enough to reproduce. Natural selection, then, provides a more compelling mechanism for adaptation and evolution than Lamarck's theories.

Some creatures, such as this leafy sea dragon fish (Phycodurus eques) have evolved adaptations that allow them to blend in with their environment (in this case, seaweed) to avoid the attention of hungry predators.

For Students & Teachers

For Teachers Only

Heritable information provides for the continuity of life.

Describe the events that occur in the cell cycle.

Explain how mitosis results in the transmission of chromosomes from one generation to the next.

In eukaryotes, cells divide and transmit genetic information via two highly regulated processes.
The cell cycle is a highly regulated series of events for the growth and reproduction of cells–

  1. The cell cycle consists of sequential stages of interphase (G1, S, G2), mitosis, and cytokinesis.
  2. A cell can enter a stage (G0) where it no longer divides, but it can reenter the cell cycle in response to appropriate cues. Nondividing cells may exit the cell cycle or be held at a particular stage in the cell cycle.

Mitosis is a process that ensures the transfer of a complete genome from a parent cell to two genetically identical daughter cells–

  1. Mitosis plays a role in growth, tissue refrain, and asexual reproduction.
  2. Mitosis alternates with interphase in the cell cycle.
  3. Mitosis occurs in a sequential series of steps (prophase, metaphase, anaphase, telophase.)

Biology Chapter 1

DNA migrates throughout the cell and interacts directly with other molecules in the cytoplasm.

DNA is translated into protein and then transcribed to RNA.

The information in DNA is transcribed to RNA and then usually translated into protein.

A-Individuals in a population of any species vary in many heritable traits.

B-Individuals with heritable traits best suited to the local environment will generally produce a disproportionate number of healthy, fertile offspring.

C-A population of any species has the potential to produce far more offspring than will survive to produce offspring of their own.

systems biology . reductionism

descent from a common ancestor . adaptation through natural selection

ensures that the variable being tested is measured without error

ensures that hypotheses can be confirmed with certainty

allows rejection of hypotheses

nonsystematic observation and analysis of data

If the animals observed require organic molecules as nutrients, then it can be concluded that all animals require organic molecules as nutrients.

Because worms lack bones, they are classified as invertebrates.

A paramecium moves by means of the rhythmic motion of its cilia.

some conceivable observation or experiment could reveal whether a given hypothesis is incorrect

the hypothesis has been proved wrong

only a controlled experiment can prove whether the hypothesis is correct or incorrect

in rephrasing an alternative hypothesis

during the formulation of a hypothesis

during initial observation(s)

explaining naturally occurring events

determining the physical causes for physical phenomena

formulating testable hypotheses in seeking natural causes for natural phenomena

that the drug seems to have little effect on viral transmission at the dosage given

nothing, because no control group was used in the test of the drug

that the drug is effective and testing on humans should begin

grow bean plants with and without sodium

look for sodium in leaf tissues using autoradiography

measure the amount of sodium in a few bean plants

is too difficult for researchers doing fieldwork

is not necessary if the scientist obtains enough background information

should always be done by changing a variable

No, it is not necessary to test only one variable per experiment, especially when time is of the essence.

As long as the experiment is repeated a sufficient number of times, it does not matter how many variables are used.

Yes, an experiment should test only one variable at a time. That way, the experiment will have to be performed only once.

a well-supported concept that has broad explanatory power

a poorly supported idea that has little backing but might be correct

not correct unless it is several years old

None of the listed responses is correct.

both negative feedback where the pathway shuts down and positive feedback where the pathway speeds up

negative feedback where the pathway does not change

negative feedback where the pathway speeds up

positive feedback where the pathway shuts down

Regardless of whether the models were placed in the beach or the inland habitat, the camouflaged model always acted as the __________ group.

Molecule, tissue, cell, organelle, organ

Community, population, ecosystem, habitat, biosphere

Organism, ecosystem, community, population, biosphere

Tissue, organ system, organ, cell, organism

transcription, translation, and protein folding

translation, transcription, and protein folding

protein folding, translation, and transcription

protein folding, transcription, and translation

are bacteria, archaea, and eukarya

are animalia, plantae, and fungi

are bacteria, archaea, and animalia

are bacteria, protists, and animalia

allows us to reduce complex systems to simpler components that are more manageable to study

starts at the global scale for studying biology

focuses on information that is seen from space

is never used in the study of biology

forming and testing hypotheses

community analysis and feedback

exploration and discovery

societal benefits and outcomes

involves chemical cycling from light energy from the sun for the production of chemical energy in food to the decomposition and the returning of chemicals to the cycle

involves chemical cycling from chemical energy in food to light energy from the sun to heat lost from the ecosystem

Female Reproductive System

The female reproductive system provides several functions. The ovaries produce the egg cells, called the ova or oocytes. The oocytes are then transported to the fallopian tube where fertilization by a sperm may occur. The fertilized egg then moves to the uterus, where the uterine lining has thickened in response to the normal hormones of the reproductive cycle. Once in the uterus, the fertilized egg can implant into thickened uterine lining and continue to develop. If implantation does not take place, the uterine lining is shed as menstrual flow. In addition, the female reproductive system produces female sex hormones that maintain the reproductive cycle.

During menopause, the female reproductive system gradually stops making the female hormones necessary for the reproductive cycle to work. At this point, menstrual cycles can become irregular and eventually stop. One year after menstrual cycles stop, the woman is considered to be menopausal.

What parts make-up the female anatomy?

The female reproductive anatomy includes both external and internal structures.

The function of the external female reproductive structures (the genital) is twofold: To enable sperm to enter the body and to protect the internal genital organs from infectious organisms.

The main external structures of the female reproductive system include:

  • Labia majora: The labia majora (“large lips”) enclose and protect the other external reproductive organs. During puberty, hair growth occurs on the skin of the labia majora, which also contain sweat and oil-secreting glands.
  • Labia minora: The labia minora (“small lips”) can have a variety of sizes and shapes. They lie just inside the labia majora, and surround the openings to the vagina (the canal that joins the lower part of the uterus to the outside of the body) and urethra (the tube that carries urine from the bladder to the outside of the body). This skin is very delicate and can become easily irritated and swollen.
  • Bartholin’s glands: These glands are located next to the vaginal opening on each side and produce a fluid (mucus) secretion.
  • Clitoris: The two labia minora meet at the clitoris, a small, sensitive protrusion that is comparable to the penis in males. The clitoris is covered by a fold of skin, called the prepuce, which is similar to the foreskin at the end of the penis. Like the penis, the clitoris is very sensitive to stimulation and can become erect.

The internal reproductive organs include:

  • Vagina: The vagina is a canal that joins the cervix (the lower part of uterus) to the outside of the body. It also is known as the birth canal.
  • Uterus (womb): The uterus is a hollow, pear-shaped organ that is the home to a developing fetus. The uterus is divided into two parts: the cervix, which is the lower part that opens into the vagina, and the main body of the uterus, called the corpus. The corpus can easily expand to hold a developing baby. A canal through the cervix allows sperm to enter and menstrual blood to exit.
  • Ovaries: The ovaries are small, oval-shaped glands that are located on either side of the uterus. The ovaries produce eggs and hormones.
  • Fallopian tubes: These are narrow tubes that are attached to the upper part of the uterus and serve as pathways for the ova (egg cells) to travel from the ovaries to the uterus. Fertilization of an egg by a sperm normally occurs in the fallopian tubes. The fertilized egg then moves to the uterus, where it implants to the uterine lining.

What happens during the menstrual cycle?

Females of reproductive age (beginning anywhere from 11 to 16 years of age) experience cycles of hormonal activity that repeat at about one-month intervals. Menstru means "monthly” – leading to the term menstrual cycle. With every cycle, a woman’s body prepares for a potential pregnancy, whether or not that is the woman’s intention. The term menstruation refers to the periodic shedding of the uterine lining. Many women call the days that they notice vaginal bleeding their “period,” “menstrual” or cycle.

The average menstrual cycle takes about 28 days and occurs in phases. These phases include:

  • The follicular phase (development of the egg)
  • The ovulatory phase (release of the egg)
  • The luteal phase (hormone levels decrease if the egg does not implant)

There are four major hormones (chemicals that stimulate or regulate the activity of cells or organs) involved in the menstrual cycle. These hormones include:

  • Follicle-stimulating hormone
  • Luteinizing hormone
  • Estrogen
  • Progesterone

Follicular phase

This phase starts on the first day of your period. During the follicular phase of the menstrual cycle, the following events occur:

  • Two hormones, follicle stimulating hormone (FSH) and luteinizing hormone (LH) are released from the brain and travel in the blood to the ovaries.
  • The hormones stimulate the growth of about 15 to 20 eggs in the ovaries, each in its own "shell," called a follicle.
  • These hormones (FSH and LH) also trigger an increase in the production of the female hormone estrogen.
  • As estrogen levels rise, like a switch, it turns off the production of follicle-stimulating hormone. This careful balance of hormones allows the body to limit the number of follicles that will prepare eggs to be released.
  • As the follicular phase progresses, one follicle in one ovary becomes dominant and continues to mature. This dominant follicle suppresses all of the other follicles in the group. As a result, they stop growing and die. The dominant follicle continues to produce estrogen.

Ovulatory phase

The ovulatory phase (ovulation) usually starts about 14 days after the follicular phase started, but this can vary. The ovulatory phase falls between the follicular phase and luteal phase. Most women will have a menstrual period 10 to 16 days after ovulation. During this phase, the following events occur:

  • The rise in estrogen from the dominant follicle triggers a surge in the amount of luteinizing hormone that is produced by the brain.
  • This causes the dominant follicle to release its egg from the ovary.
  • As the egg is released (a process called ovulation) it is captured by finger-like projections on the end of the fallopian tubes (fimbriae). The fimbriae sweep the egg into the tube.
  • For one to five days prior to ovulation, many women will notice an increase in egg white cervical mucus. This mucus is the vaginal discharge that helps to capture and nourish sperm on its way to meet the egg for fertilization.

Luteal phase

The luteal phase begins right after ovulation and involves the following processes:

  • Once it releases its egg, the empty ovarian follicle develops into a new structure called the corpus luteum.
  • The corpus luteum secretes the hormones estrogen and progesterone. Progesterone prepares the uterus for a fertilized egg to implant.
  • If intercourse has taken place and a man's sperm has fertilized the egg (a process called conception), the fertilized egg (embryo) will travel through the fallopian tube to implant in the uterus. The woman is now considered pregnant.
  • If the egg is not fertilized, it passes through the uterus. Not needed to support a pregnancy, the lining of the uterus breaks down and sheds, and the next menstrual period begins.

How many eggs does a woman have?

During fetal life, there are about 6 million to 7 million eggs. From this time, no new eggs are produced. At birth, there are approximately 1 million eggs and by the time of puberty, only about 300,000 remain. Of these, only 300 to 400 will be ovulated during a woman's reproductive lifetime. Fertility can drop as a woman ages due to decreasing number and quality of the remaining eggs.

Last reviewed by a Cleveland Clinic medical professional on 01/19/2019.


  • The American College of Obstetricians and Gynecologists. Your Changing Body: Puberty in Girls (Especially for Teens). Accessed 2/5/2019.
  • healthdirect. Female reproductive system. Accessed 2/5/2019.
  • US Department of Health and Human Services, Office on Women's Health. Menopause. Accessed 2/5/2019.
  • Planned Parenthood. Reproductive and Sexual Anatomy. Accessed 2/5/2019.
  • Centers for Disease Control and Prevention. Women's Reproductive Health. Accessed 2/5/2019.
  • Merck Manual. Menstrual Cycle. Accessed 2/5/2019.

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Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Related Institutes & Services

Ob/Gyn & Women's Health Institute

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Environmental Science Exam 2

The next step in this story would likely be that this woman and her sister ________.

A) started a full-scale garden, digging the soil and enriching it with food wastes

B) began to save, sort, and name different types of seeds

C) began to seek out old middens to find and eat the things growing there

D) began to deliberately plant seeds near their village to make food gathering easier in the future

A) organic matter and minerals

B) mineral content and water saturation

D) water, organic matter, and minerals

A) Native grasses were removed.

B) Wheat was grown exclusively in the area.

C) A prolonged drought struck the area.

A) The CRP is a policy that makes it illegal to plant the same crop on a piece of land three years in a row.

B) The CRP provides grants to farmers willing to use contour farming.

C) The CRP imposes financial penalties on farmers who do not employ shelterbelts in areas prone to wind erosion.

A) a diet that substitutes chicken for other protein sources

B) a diet consisting of equal percentages of meat and vegetables

C) a diet heavily dependent on meat

A) are preferentially eaten by herbivorous animals

B) are genetically modified by animals

C) are pollinated by animals

D) decrease biodiversity in an area

B) the tundra shifting northward

C) hunting of the polar bear by the Inuit people

D) fires in the taiga and tundra

B) the problems with monoculture

C) the results of an invasive species

D) the effects of pollution

A) cowbirds are an invasive species that is rapidly increasing

B) habitat fragmentation makes it easier for cowbird parasitism to occur

C) overharvesting in the open fields has driven the cowbirds into the woodlands

D) climate change is reducing nest site availability

A) international trade in protected species to aid in times of economic hardship

B) endangered species to be hunted as long as records are kept of numbers and sex of individuals taken

C) landowners to harm a protected species in one area if they protect it in another

D) landowners to kill endangered species for food if necessary

Being interested in native butterflies, you include the native caterpillar host plants of several butterflies in your annual landscape design. You are happy to see that first caterpillars and later butterflies appear in your yard. However, the butterflies tend to disperse out of your yard. To keep the butterflies in your garden, an urban wildlife specialist suggests you ________.
Read the following scenario and answer the questions below.

A) try to introduce predators of the butterflies

B) place pans of honey solution around your yard to feed the butterflies

C) introduce native flowering plants the adult butterflies need for nectar, their main food

D) ask the neighbors to refrain from planting "butterfly plants" in their yards

A) an increase in herbivorous insects and the small predators that eat them

B) competition between the lawn grass and the new species that invade the area

C) an increase in pollinating insects visiting your lawn and gardens

D) an increase in bird species in your yard

A) plant more host plants in several different areas but otherwise do nothing

B) catch and kill the predators and parasites by hand

C) spray pesticides on the plants to control the predators

D) give up on the butterfly species you encouraged and try to attract new species.

A) increasing the populations of butterflies

B) decreasing the number of predatory animals and insects

C) increasing the biodiversity of soil organisms, including decomposers

D) making habitats for pollinators

A) Water runoff is decreased.

B) Biodiversity is increased.

C) Crop productivity is greatly increased because of the rich soil.

D) CO2 levels remain appropriate within the atmosphere.

B) It is a secondary forest.

C) It is an old growth forest

A) It has allowed too much clear-cutting.

B) It has focused attention on forests rather than grasslands.

C) It has allowed too few fires to burn in forests.

B) removal of air pollution

C) prevention of soil erosion

A) using a selection system to get uneven-aged stands

B) leaving several small areas uncut in the middle of a clear-cut

C) the shelterwood approach

A) pollution, aggression, technology

B) population, adaptation, total fertility rate

C) population, affluence, technology

A) affluence and technology

B) rates of birth, death, immigration, and emigration

C) availability of medical procedures

A) rapid population growth is a short-term phenomenon between the drop in death rate and the drop in birth rate in a population

B) populations will suffer a temporary drop in numbers as birth rates drop below death rates until the death rate is brought down

C) population growth will accelerate as a country stays industrialized for longer periods of time

A) At a TFR of 2.1, the population will be shrinking.

B) The value means that two children plus a fraction to compensate for the death of offspring will replace the average male and female in the population.

C) The value means that the population is growing slowly because 2.1 − 2.0 = +0.1.

A) disease is a limiting factor of population growth so impact on resources is ultimately minimal

B) geologists have shown that Earth regenerates resources as fast as they are discovered and used

C) population size must be kept low to prevent the damage caused by erosion, pollution, and loss of groundwater resources for agriculture

A) It skewed toward more females resulting in more reproduction per person in the population.

B) It is evenly distributed between males and females.

C) It is skewed toward more males causing a slowing in population growth.

A) The total population decreases.

B) TFR will increase since women are able to stay at home rather than work in the fields to grow food.

C) Population growth rate slows.

A) sex ratio, to denote number of mating pairs so as it shifts from 50/50 there is a reduction in impact

B) sensitivity, to denote how sensitive a given environment is to these pressures causing more damage for sensitive habitats

C) sensitivity, to denote how sensitive a given human population is to population control thereby reducing its impact

Brain Basics: The Life and Death of a Neuron

Until recently, most neuroscientists thought we were born with all the neurons we were ever going to have. As children we might produce some new neurons to help build the pathways - called neural circuits - that act as information highways between different areas of the brain. But scientists believed that once a neural circuit was in place, adding any new neurons would disrupt the flow of information and disable the brain&rsquos communication system.

In 1962, scientist Joseph Altman challenged this belief when he saw evidence of neurogenesis (the birth of neurons) in a region of the adult rat brain called the hippocampus. He later reported that newborn neurons migrated from their birthplace in the hippocampus to other parts of the brain. In 1979, another scientist, Michael Kaplan, confirmed Altman&rsquos findings in the rat brain, and in 1983 he found neural precursor cells in the forebrain of an adult monkey.

These discoveries about neurogenesis in the adult brain were surprising to other researchers who didn&rsquot think they could be true in humans. But in the early 1980s, a scientist trying to understand how birds learn to sing suggested that neuroscientists look again at neurogenesis in the adult brain and begin to see how it might make sense. In a series of experiments, Fernando Nottebohm and his research team showed that the numbers of neurons in the forebrains of male canaries dramatically increased during the mating season. This was the same time in which the birds had to learn new songs to attract females.

Why did these bird brains add neurons at such a critical time in learning? Nottebohm believed it was because fresh neurons helped store new song patterns within the neural circuits of the forebrain, the area of the brain that controls complex behaviors. These new neurons made learning possible. If birds made new neurons to help them remember and learn, Nottebohm thought the brains of mammals might too.

Other scientists believed these findings could not apply to mammals, but Elizabeth Gould later found evidence of newborn neurons in a distinct area of the brain in monkeys, and Fred Gage and Peter Eriksson showed that the adult human brain produced new neurons in a similar area.

For some neuroscientists, neurogenesis in the adult brain is still an unproven theory. But others think the evidence offers intriguing possibilities about the role of adult-generated neurons in learning and memory.


The Architecture of the Neuron

The central nervous system (which includes the brain and spinal cord) is made up of two basic types of cells: neurons (1) and glia (4) & (6). Glia outnumber neurons in some parts of the brain, but neurons are the key players in the brain.

Neurons are information messengers. They use electrical impulses and chemical signals to transmit information between different areas of the brain, and between the brain and the rest of the nervous system. Everything we think and feel and do would be impossible without the work of neurons and their support cells, the glial cells called astrocytes (4) and oligodendrocytes (6).

Neurons have three basic parts: a cell body and two extensions called an axon (5) and a dendrite (3). Within the cell body is a nucleus (2), which controls the cell&rsquos activities and contains the cell&rsquos genetic material. The axon looks like a long tail and transmits messages from the cell. Dendrites look like the branches of a tree and receive messages for the cell. Neurons communicate with each other by sending chemicals, called neurotransmitters, across a tiny space, called a synapse, between the axons and dendrites of adjacent neurons.

The architecture of the neuron.

There are three classes of neurons:

  1. Sensory neurons carry information from the sense organs (such as the eyes and ears) to the brain.
  2. Motor neurons control voluntary muscle activity such as speaking and carry messages from nerve cells in the brain to the muscles.
  3. All the other neurons are called interneurons.

Scientists think that neurons are the most diverse kind of cell in the body. Within these three classes of neurons are hundreds of different types, each with specific message-carrying abilities.

How these neurons communicate with each other by making connections is what makes each of us unique in how we think, and feel, and act.


The extent to which new neurons are generated in the brain is a controversial subject among neuroscientists. Although the majority of neurons are already present in our brains by the time we are born, there is evidence to support that neurogenesis (the scientific word for the birth of neurons) is a lifelong process.

Neurons are born in areas of the brain that are rich in concentrations of neural precursor cells (also called neural stem cells). These cells have the potential to generate most, if not all, of the different types of neurons and glia found in the brain.

Neuroscientists have observed how neural precursor cells behave in the laboratory. Although this may not be exactly how these cells behave when they are in the brain, it gives us information about how they could be behaving when they are in the brain&rsquos environment.

The science of stem cells is still very new, and could change with additional discoveries, but researchers have learned enough to be able to describe how neural stem cells generate the other cells of the brain. They call it a stem cell&rsquos lineage and it is similar in principle to a family tree.

Neural stem cells increase by dividing in two and producing either two new stem cells, or two early progenitor cells, or one of each.

When a stem cell divides to produce another stem cell, it is said to self-renew. This new cell has the potential to make more stem cells.

When a stem cell divides to produce an early progenitor cell, it is said to differentiate. Differentiation means that the new cell is more specialized in form and function. An early progenitor cell does not have the potential of a stem cell to make many different types of cells. It can only make cells in its particular lineage.

Early progenitor cells can self-renew or go in either of two ways. One type will give rise to astrocytes. The other type will ultimately produce neurons or oligodendrocytes.


Once a neuron is born it has to travel to the place in the brain where it will do its work.

How does a neuron know where to go? What helps it get there?

Scientists have seen that neurons use at least two different methods to travel:

  1. Some neurons migrate by following the long fibers of cells called radial glia. These fibers extend from the inner layers to the outer layers of the brain. Neurons glide along the fibers until they reach their destination.
  2. Neurons also travel by using chemical signals. Scientists have found special molecules on the surface of neurons -- adhesion molecules -- that bind with similar molecules on nearby glial cells or nerve axons. These chemical signals guide the neuron to its final location.

Not all neurons are successful in their journey. Scientists think that only a third reach their destination. Some cells die during the process of neuronal development.

Some neurons survive the trip, but end up where they shouldn&rsquot be. Mutations in the genes that control migration create areas of misplaced or oddly formed neurons that can cause disorders such as childhood epilepsy. Some researchers suspect that schizophrenia and the learning disorder dyslexia are partly the result of misguided neurons.

Some neurons migrate by riding along extensions (radial glia) until they reach their final destinations.


Once a neuron reaches its destination, it has to settle in to work. This final step of differentiation is the least well-understood part of neurogenesis.

Neurons are responsible for the transport and uptake of neurotransmitters - chemicals that relay information between brain cells.

Depending on its location, a neuron can perform the job of a sensory neuron, a motor neuron, or an interneuron, sending and receiving specific neurotransmitters.

In the developing brain, a neuron depends on molecular signals from other cells, such as astrocytes, to determine its shape and location, the kind of transmitter it produces, and to which other neurons it will connect. These freshly born cells establish neural circuits - or information pathways connecting neuron to neuron - that will be in place throughout adulthood.

But in the adult brain, neural circuits are already developed and neurons must find a way to fit in. As a new neuron settles in, it starts to look like surrounding cells. It develops an axon and dendrites and begins to communicate with its neighbors.

Stem cells differentiate to produce different types of nerve cells.


Although neurons are the longest living cells in the body, large numbers of them die during migration and differentiation.

The lives of some neurons can take abnormal turns. Some diseases of the brain are the result of the unnatural deaths of neurons.

- In Parkinson&rsquos disease, neurons that produce the neurotransmitter dopamine die off in the basal ganglia, an area of the brain that controls body movements. This causes difficulty initiating movement.

- In Huntington&rsquos disease, a genetic mutation causes over-production of a neurotransmitter called glutamate, which kills neurons in the basal ganglia. As a result, people twist and writhe uncontrollably.

- In Alzheimer&rsquos disease, unusual proteins build up in and around neurons in the neocortex and hippocampus, parts of the brain that control memory. When these neurons die, people lose their capacity to remember and their ability to do everyday tasks. Physical damage to the brain and other parts of the central nervous system can also kill or disable neurons.

- Blows to the brain, or the damage caused by a stroke, can kill neurons outright or slowly starve them of the oxygen and nutrients they need to survive.

- Spinal cord injury can disrupt communication between the brain and muscles when neurons lose their connection to axons located below the site of injury. These neurons may still live, but they lose their ability to communicate.

One method of cell death results from the release of excess glutamate.

Macrophages (green) eat dying neurons in order to clear debris.

Hope Through Research

Scientists hope that by understanding more about the life and death of neurons they can develop new treatments, and possibly even cures, for brain diseases and disorders that affect the lives of millions of Americans.

The most current research suggests that neural stem cells can generate many, if not all, of the different types of neurons found in the brain and the nervous system. Learning how to manipulate these stem cells in the laboratory into specific types of neurons could produce a fresh supply of brain cells to replace those that have died or been damaged.

Therapies could also be created to take advantage of growth factors and other signaling mechanisms inside the brain that tell precursor cells to make new neurons. This would make it possible to repair, reshape, and renew the brain from within.

For information on other neurological disorders or research programs funded by the National Institute of Neurological Disorders and Stroke, contact the Institute's Brain Resources and Information Network ( BRAIN ) at:

Prepared by:
Office of Communications and Public Liaison
National Institute of Neurological Disorders and Stroke
National Institutes of Health
Bethesda, MD 20892

NINDS health-related material is provided for information purposes only and does not necessarily represent endorsement by or an official position of the National Institute of Neurological Disorders and Stroke or any other Federal agency. Advice on the treatment or care of an individual patient should be obtained through consultation with a physician who has examined that patient or is familiar with that patient's medical history.

All NINDS-prepared information is in the public domain and may be freely copied. Credit to the NINDS or the NIH is appreciated.

12 Answers 12

Using some limits from other answers - I will restrict myself by saying the creature must grow, be conscious, reproduce, and eventually die.

It is my own opinion that this would be possible - though I do not believe such a creature would ever actually evolve in the real universe. It requires many unique complex processes and requirements because of its niche environment(space), and to reach this complexity, there should be less complex organisms which it could evolve from. This is a problem because there isn't really another similar environment that would easily provide some sort of evolution "cross-over", though I could be wrong.

The only input to the system is sunlight, so the creature needs all other materials to be carried with it. This will have an impact on all the biological processes of the creature. The creature I imagine is actually quite close to @Envite's answer when I think about it.

The creature starts with being born. It has a bunch of "working materials" around it at the start - this is because of its parent. Other than that, there is only the emptiness of space and sunlight.

The creature consumes the material and starts to grow - using the sunlight as its source of fuel. It could be a complex creature, capable of great thought (though it has nobody to teach it anything) or it could be a very simple creature.

Eventually, it has consumed all the material. It self-replicates its child, probably into an egg form, and as it dies it releases (bacteria/chemicals/whatever) that it created during its lifetime which turn it into usable material once again.

The shell of the egg protects it from the bacteria, and the bacteria dies. Then the child is born and the cycle begins again.

If the creature needs to grow and reproduce, a matter is required to build the new parts. Just energy itself is not enough. Because of that, plants need minerals and nitrogen from the soil and also take oxygen, carbon and hydrogen from the surrounding air.

If no growth or reproduction is required, a living (= running typical metabolism of the living organism, capable of regeneration and possibly limited growth with expense of some other part dying and decomposing) system can be self-contained. A single usual plant would probably survive in a closed system with enough sunlight, sufficient initial amount of water and minerals and some bacteria and fungi to convert the dead parts into usable minerals.

Planet Earth as a whole (as stated in the Gaia Theory in its stronger form) is a living being that lives by feeding only solar energy, and keeping all other resources in a closed circuit, gravity bound. So answer is yes.

This strongly depends on your definition of "Life".

The most common definition is the biological-life in which living systems always depend on nucleic acides.

Since there is no unequivocal definition of life, the current understanding is descriptive. Life is considered a characteristic of something that exhibits all or most of the following traits .. (click link for further information) - Wikipedia - Life/Definition

There are theories of lifeforms which do not depend on carbon (As we do).

But while reading these theories, you'll notice that those who set up these theories, tried to recreate life as we know on different chemistry but did't really looked "how life else could work".

For example, I remember this one episode (Dont know the #, sry) of Star Trek - The next generation in which they met a giant crystal which was floating in space. This crystal had some kind of consciousness and had to consume energy to stay alive. In the episode the creature consumed the warp-field or something, not sure. But you see the point I guess.

I do not think life has to be 'biological' as we know. My personal definition of life, which doesn't really go against the common one (due there is none), is that living things have these:

  • consciousness (doesn't mean awareness of themself, but can)
  • ability to consume and create things ( as like metabolism )
  • ability to replicate under specific circumstances

According to this and Abiogenesis in theory life could develop almost everywhere. The point why it does not is the razerblade problem. Try to stack several razerblades on each other. they'll collapse. Just under rare circumstances it's possible that they do not, and that's probably the point of life.

We already found amino acids on asteroids, so this concept is not that hypotetical, even if it's not proven at the point.

If you look at the lowest developed animals or bacteria we know, like Trichoplax (which btw is different than any other animal we know), you will find structures and metabolism which are really basic and oftn don't need atmosphere to work. So the atmosphere itself is not the problem, the pressure isn't either due a evolution in space-low pressure literally evovles with this pressure.

A lack of nutrient isn't probable too. Look at corals and other sessility animals you'll see that they do not, or almost not, need any nutrients to "stay alive" but to grow and replicate. This principe supports life in areas where almost no nutrients exist like in space. (Even in space, there are particles which could be consumed).

So, if you accept this definitions, nothing stops you from creating any fictional form of life which fit's this requierements.

And as always, stay plausible and keep causality up.

Life only depending on light is implausible. Just as said before, your lifeform must create matter out of light wich seems to be impossible. But as I said, even in space there are atoms and molecules which could be used as nutrients, even if they're very rare.

This means your direct question must be answered with NO, but with a slight change it is possible.