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In my understanding, the evolutional function of berries is to be eaten and pood out somewhere else, so that the seeds of the plant spread. Is this so? Then why are some berries poisonous?
While poison affects not every organism equally, plants did develop some poisons to avoid being eaten. However, if you look at the great multitude of so-called secondary metabolites, most of them are poisonous to either viruses, bacteria, fungi or other microorganisms, or insects, or even other plants. Plant evolution just hasn't had time to adapt to humans.
So, if some substance from plants is a poison to us, it's accidentally so, and the target was another organism. Examples: nicotine is first and foremost an insecticide, nematistat, and herbicide; aconitine, atropine, caffeine are insecticides; many essential oils (causing allergies in human) are antimicrobial and so on.
This has also to do with the fact that nerve cell physiology has not much changed since they developed in the first multi-celled animals, and poisons for insect nerves have at least some effect on human nerves.
Smooth sumac has edible berries and poisonous but medicinal leaves
A thicket of smooth sumac retained some of its berries in January, though most of them were gone. Smooth sumac is well known for its brilliant red fall foliage and its deep red berries.
Smooth sumac, Rhus glabra, is the only shrub or tree that is native to all of the 48 contiguous states. It is a woody shrub that grows three to six feet tall in the Rocky Mountains, but 10 to 20 feet tall elsewhere. The genus Rhuscontains about 35 species that are native to North America, but only one other species is native to Colorado—fragrant sumac, Rhus trilobata. Both glabra and trilobata have rhizomes that send up young stems and this form of asexual reproduction produces clones of sumac.
Smooth and fragrant sumac are easy to distinguish. A trilobata leaf develops as three completely separated lobes, while a glabra leaf is compound, one to two feet long, with 11 to 31 pointed leaflets per leaf—these remind me of the leaves of ferns. The upper branches of smooth sumac are short and crooked.
Inviting red berries of smooth sumac remain on the twigs through winter, available to birds and mammals. Photo by Jeff Mitton.
Sumac species are dioecious, meaning that a plant is either male or female. The flowers, which range from green to white, are arranged in upright clusters called drupes. Male flowers have 5 petals and 5 yellow anthers, with a ring of nectaries below the anthers to reward pollinators. Female flowers also have 5 petals but a single style which splits into three lobes at the tip. A drupe consists of 100 to 700 flowers and a fertilized female flower develops into a berry with a single seed—so only females produce berries.
Approximately 250 species of sumac are known, from all of the continents, and they follow one simple, very handy generalization. Species with red berries, including smooth and fragrant sumac, produce edible berries, while species with white berries, including poison ivy, have poisonous berries. Native Americans were aware that red sumac berries were edible—analyses of remains of human feces contained sumac seeds dated to 1,200 CE at Antelope House in Canyon de Chelly and from at least 2,000 years ago at Puebloan sites across the Four Corners area. Berries were frequently eaten raw but also made into a refreshing lemonade. Young twigs could be plucked from a shrub, peeled and eaten as a crunchy salad.
Deer, small mammals and numerous species of birds consume sumac berries from both smooth and fragrant sumac.
Chemical defenses in the leaves of sumacs are diverse and potent. They contain tannins, phytols, and three different compounds related to gallic acid which have antimicrobial activities. The arsenal of chemical defenses is so effective that only the sumac leaf beetle, Blepharida rhois, can eat the leaves of smooth sumac and fragrant sumac. As this specialist feeds it drills many tiny holes in the leaves. A larva concentrates the sumac’s chemical defenses in its feces and then coils the fetid feces on its back, forming a fecal shield that deters avian predators.
Approximately 250 species of sumac are known, from all of the continents, and they follow one simple, very handy generalization."
Native Americans made good use of the chemical defenses that evolved to deter herbivores. A rinse made from boiled berries was applied to stop bleeding after childbirth. Tea prepared from leaves was used to treat asthma and diarrhea. Roots were boiled to extract an antiseptic applied to wounds and ulcers. Juice extracted from roots was believed to cure warts. Tea prepared from green twigs was used to treat tuberculosis.
Ute basket weavers preferred the supple twigs of fragrant sumac for ceremonial baskets, while willow branches could be used to weave coarser working baskets.
A surprising range of pigments were extracted from sumac for dyeing baskets and blankets. Navajo used fermented berries to create an orange-brown dye, while a different extraction from berries produced red. Crushed twigs and leaves yielded a black dye when mixed with ochre mineral and the resin of pinyon pine. Roots produced a yellow dye and a light-yellow dye could be made from the pulverized pulp of stems. Tannins extracted from leaves produce a brown dye.
Smooth sumac and fragrant sumac have always been conspicuous in the fall, but now they seem more apparent to me. They remind me of the Native Americans that first occupied this land, simply because they were such important sources of food, medicines, weaving materials and dyes.
Examples of Poisonous Plants
Poisoning from plants is a common fear but an extremely rare event. It is true that a few plant species in certain localities can produce serious toxicity like dander (Nerium oleander), foxglove (Digitalis purpurea), jequirity pea (Abrus precatorius), castor bean (Ricinus communis), water hemlock (Cicuta maculata), Jerusalem cherry (Solanaum pseudocapsicum), free tobacco (Nicotina glauca), jimsonweed (Datura stramonium), autumn crocus (Colchicum autumnale) and hepatotoxic mushrooms (Amantia phalloides and A. virosa).
In most cases, exceptional circumstances are required to produce severe poisoning. Even then, each year, a few deaths from plant poisoning do occur all over the world.
Example # 1. Yew (Taxus canadensis) :
This is a very common ornamental hedge. All parts of Taxus except the red fruit contain poisons i.e. taxine A and taxine B within 1 hour of consumption it causes severe gastroenteritis which may be followed by convulsions, shock, coma and death.
It has also been classified as cardiotoxic. It has been recognized as an abortifacient by many women.
Example # 2. Castor Bean (Ricinus communis):
This plant contains ricin, a potent cellular protein toxin. Its seeds containing the toxin can be swallowed whole without injury, if, however, the seeds are crushed and the toxin is released, then severe gastroenteritis results. It may lead to CNS depression, cardiac dysrhythimias, coma and death.
Example # 3. Rosary Pea (Abrus precatorius):
It produces a toxin called abrin which is similar to ricin. It inhibits protein synthesis. All parts of the plant are toxic with seeds containing the higher amount of toxin.
Example # 4. Lily of the Valley (Convallaria majalis):
Convallarin and convallotoxin are found in this common garden plant. Convallotoxin and other glycosides act by inhibiting the enzyme Na + /K + ATPase, Convallaria causes bradycardia and uncoordinated heartbeat.
Example # 5. Toxglove (Digitalis purpurea):
It produces a toxin called as “digitoxin” Digitoxin has been very valuable in medicine, but while it has saved many lives, it has also produced significant toxicity. It damages kidney. Many murders have been committed with digitalis as vehicle of death.
Example # 6. Oleander (Nerium oleander):
Its poisoning is based on cardiac glycoside. It predominantly causes GI and cardiac symptoms. Even meat roasted on the twigs of this plant becomes poisonous. Bees sometime use oleander pollen for their honey. The honey too, prepared in this manner has been found to be poisonous.
Example # 7. Monkshood (Aconitum napellus):
This plant is also known as wolfsbane. It is used by some as an herbal medicine under the name of aconite. It contains two alkaloid toxins i.e. aconine and aconitine. Upon ingestion, cardiac and neurologic symptoms have been reported. Several French recruits died from eating monkshood while on a training exercise during World War – I.
Example # 8. Black Hellebore (Helleborus niger) :
This plant is also known as henbane. The entire plant is poisonous and contains hellebrin, helleborin, and saponins. It is a GI irritant, but its major effect is death from cardiac arrest.
Example # 9. Death Camas (Zygadenus venenosus) :
They are called as grayanotoxins and include veratrine and zygadenine. They cause bradycardia and hypotension as well as cholinergic symptoms namely salivation, lacrimation, rhinorrhea and emesis. They have been mistaken by campers for onion.
Example # 10. Azalea (Rhododendron) :
These plants are omnipresent. They share many properties. They produce a specific poison called andromedotoxin. This toxin causes GI stress, respiratory difficulty and bradycardia. Some birds eat these bushes which renders their flash poisonous.
Example # 11. Mushrooms :
Five thousand mushroom species are known to occur in United States alone. Approximately 2% of these species are toxic. Poisonous mushrooms contain toxins that are as diverse as mushrooms, themselves.
The mushroom portion of the fungus is the reproductive structure that grows from underground mycelium as a densely packed cap and stipe of interwoven hyphal strands. This structure contains the spores that germinate and form new mycelia. Variation in size, shape, color, spore and other microscopic structures aids in the identification of mushroom species.
There are about eight groups of compounds secreted by different species of mushrooms:
i. Cyclopeptide group – Amantia phalloides., A verna, A. virosa, A. bisoporegera and Galerina sp.
ii. Monomethyl hydrazine group – Amantia muscaria and A. patherina
iii. Coprine group – Gyromitra sp.
iv. Muscarine group – Clitocybe and Inocybe sp.
v. Ibotenic acid and muscimol group – Coprimus sp.
vi. Hallucinogen group – Psilocybe, Panaeolus, Gymnopilus
vii. Gastrointestinal group – Chlorophyllum molybditis
viii. Renal failure group – Cortinarius sp.
The cyclopeptide amatoxins of Amantia and Galerina can cause severe hepato­renal dysfunction. A phalloides is the prominent European poisonous mushroom. Group II mushrooms cause gastritis, less often hemolysis, hepatorenal dysfunction, convulsions and death follows ingestion. Coprine mushrooms of group III cause hyperacefaldehydemia. Muscarine mushrooms are reported to secrete muscarine.
TI causes cholinergic excess syndrome within 30 minutes. Ibotenic acid species (A. muscaria) that contain psychoactive isoxazole derivatives, produce hallucinations. They cause muscle spasm, confusion, intoxication drowsiness and sleep.
The main toxin of hallucinogenic mushrooms is psilocybin. This has lysergic acid diethylamide like properties and produce alterations in autonomic function, motor reflexes, behavior and perception gastrointestinal weakness, nausea, vomiting and diarrhea.
Example # 12. Atropa Belladonna (Deadly nightshade):
All parts of Atropa are dangerous including roots, leaves and berries. Berries contain the highest content of toxic alkaloids. These are known as atropine, hyoscine and hyoseyamine and refers to the practice during Renaissance of placing an extract of Atropa inorder to achieve dilated pupils, regarded by many as the attractive feature.
Example # 13. Datura Stramonium (Jimsonweed):
Jimsonweed is also called as thornapple, stink weed and Devil’s trumpet. It contains all the three alkaloids as described above. Severe cases may lead to loss of sight, convulsions, coma and death. Many soldiers died after eating this plant when famine broke out in 1666 in the early American colony, Jamestown in Virginia.
Example # 14.Mandragora Officinarum (Mandrake):
This plant, in addition to atropine and hyoseyamine, contains momdragorin which is considered to promote fertility and had aphrodisiac properties. It was also associated with witchcraft and women, who possessed mandrake were executed in 17 th century in Germany.
Example # 15. Neurotoxic Plants :
The toxins found in this plant are piperidine alkaloids, coniine and gamma coniceine. Their primary lethal consequences are respiratory failure. They also produce nicotinic effects viz. salivation, mydriasis, tachycardia followed by bradycardia. Pluto, the great Greek philosopher has described the death of Socrates due to hemlock.
Water hemlock is a weed commonly found along lakes and streams. Its toxin is known as cicutoxin that specifically works upon brain and spinal cord. It causes rapid onset of status epilepticus.
The red Indians in Amazon and South America dip their arrows with this poison which paralyzes the skeletal muscles of their prey. Death results from respiratory failure.
Example # 16. Cyanogenic Plants:
All those plants that are able to form cyanide under certain conditions are called as cyanogenic plants. Most cyanogenic substances are glycosides-meaning thereby that a carbohydrate moiety is part of their structure. Fortunately the cyanogens are not found in fruits but present in leaves, stem and bark. Examples are apple, apricot, cherry, peach, and black berry.
i. Hydrangea Paniculata:
Hydrangea contains two cyanogenic glycosides known as hydrangin and amygdalin. Symptoms of poisoning are nausea and gastroenteritis.
This fruit contains amygdalin. Interestingly amygdalin has become celebrated as an alleged cancer cure and is most commonly called as laetrile. Laetrile is more likely to cause harm rather than benefit.
iii. Cassava (Manihot esculenta):
This is a common dietary component in many parts of the world. It contains a cyanogenic glycoside known as linamarin. Tropical ataxic neuropathy has been observed in Nigeria and epidemic spastic paraperesis has been observed in certain parts of equatorial Africa.
Example # 17. Hepatotoxic Plants:
Akee when unripe, contains hypoglycin, a compound believed to be teratogenic and a cause of toxic hypoglycemic syndrome (also called Jamaican vomiting sickness). Akee is a staple food of Jamaica and British West Indies. Raw or spoiled fruit is to be avoided.
Example # 18. Solanaceous Plants:
About 1700 species of these plants are known till date. They all contain salanaceous alkaloids. Many solanaceous alkaloids contain the same basic aglycone but differ in the number and type of carbohydrate molecules. Solanine occurs in the common potato. Solanum tuberosum. Levels of solanine above 20 ppm are dangerous. Solanine is a cholinesterase inhibitor. It causes cholinergic symptoms such as salivation, trembling, progressive weakness and paralysis.
It sounds like it may have been a small Mulberry tree. I grew up with them. They are edible.
Which could explain why you were put off by the smell, especially if you were expecting it to smell like a blackberry.
An example of something that looks like an edible berry (tomato) but is in fact poisonous, is the nightshade plant (bella donna). The fruits look like little green tomatoes and are actually related to tomatoes, which is why hundreds of years ago, people where afraid to eat tomatoes.
Thank you! The description of the mulberry plant at Wikipedia seems to match what I saw. The article says that the sap is a hallucinogen. Perhaps a scientific investigation is in order. Also, it says mulberry is known as Toot in the middle east. My guess is they named it after eating too many on an empty stomach
In the case of the nightshade, I wonder if it is poisonous to all critters or just some of us. Why would a plant make a tempting poisonous fruit? Sooner or later animals will learn to spot the deception and then the seeds won't be spread in the customary fasion. Right?
Before you go off the deep end consider that a lot of foods we eat contain small amounts of plant toxins. Consider rhubarb - consuming the leaves will make you ill, but the petiole (the celery-like part) is edible - at least in the sense that it doesn't kill you. The list goes on and on:
This is very likely why humans over time selectively grew plants with lower levels of plant toxins. The wild cousins of domesticated plants often have higher levels of these toxins - which the plant uses as a defense against herbivory. Domesticated plants are practically defenseless in some cases.
haha. I haven't had rhubarb but I've never heard anything positive about it. Thank you for that helpful link. It makes sense that plants would have a whole arsenal of chemical weapons to keep things like cows, goats, insects, fungi, etc. from munching on them. I understand that caffeine and cocaine are examples of such chemical weapons, although they give humans a pleasant buzz if taken moderately. I was not aware that the concentration of toxins could vary so much depending on the environmental stress the plant is under. That's interesting.
What I'm concerned about is the possibility of some super-toxic berry that kills you after eating two or three. That seems like overkill to me, from a self-defense perspective. I doubted that such plants existed, but then I found this semi-reliable looking web page that lists all sorts of common plants that are supposedly very dangerous:
However, this other equally reliable looking page, from Children's Hospital of Philadelphia, lists some of the same plants as hardly toxic in small quantities, so I don't know who is telling the truth:
The tamu site is Texas A&M's link to their Botany Department. chop.edu is the Children's Hospital.
The folks at tamu are reporting the lab findings and concentrations found in lab extractions.
chop is reporting clinical observations. The two are valid science.
Most toxic higher plants when eaten do things like:
1. burn your mouth and throat - oxalates in "dumb cane' - Dieffenbachia spp. are an example.
2. taste really awful - Rhododendron leaves
Clinical reports often find that kids only eat a portion of a foul-tasting leaf, then parents go beserk, the kid gets sick and the clinicians have to deal with it.
The reasons why the two reports vary are several things. Foods already in the stomach bind with nasty 'anti-nutrients' reducing their effect. Gastric enzymes may alter part of the toxin molecule rendering it less nasty. Kids are not going to chow down on some that tastes god-awful, so the total amount of toxin is less than it might otherwise be. On the other hand, the lab person isolates the stuff and goes through a lot of steps to extract the toxin. Your body does the opposite with a lot of toxins.
However, severe and fatal poisonings are still reported from toxic higher plant ingestion, but they are not common.
But. IMO For deadly: The winner is Basidomycetes - 'mushrooms and toadstools' . For example, George Washington Hosptial in Washington DC had a doc on staff in the 50's and 60's who really knew mushroom-ology. The reason was that DC has thousands of European Embassy people. People from Europe go 'shroom gathering. The nasty species over here look like the tasty table species in Central Europe. Voila - embassy staff presenting at GW violently ill the day after a picnic in Rock Creek Park. He kept photos of the usual suspects (like Amonita) on the wall so he could get an idea of what the patients had eaten. I used to bring in specimens for his 'herbarium' when I was doing other field work.
The embassies now train staff NOT to eat wild mushrooms but rather, buy their mushrooms at the International Safeway downtown - if it is still there.
Don’t you know that you’re toxic?
First, how do plants poison the pulp? Plants produce a range of chemical compounds, some of which have no apparent function in primary life-maintaining processes and so are called secondary compounds.
Potentially poisonous secondary compounds are produced either in the course of development from seed to adult plant, or in direct response to attacks from plant-eaters.
Poisons in fruit pulp are typically produced during development. Unripe fruit is often toxic to protect immature seeds from attack or premature dispersal, but ripe fruit with mature seeds can also be poisonous.
So how do we explain fruit that remains poisonous even when it’s ripe and ready for dispersal? One theory is that a low level of poison in fruit encourages fruit-eating animals to move away from the parent plant (avoiding additional poison), therefore carrying seeds further away.
In some cases toxins cause constipation, ensuring that seeds stay longer in the gut and so increasing the distance they are carried. In other cases – think of prunes – they act as laxatives to ensure the quick passage of seeds with minimal time for seed damage during digestion.
There is some evidence for these hypotheses, but they’re not the full story.
ELI5 - Why can birds & other animals eat berries that are poisonous & potential fatal to humans?
Because they have different physiologies to us. For instance, they may produce different chemicals in their livers which breaks the poison down into chemicals which aren't poisonous to them.
There are things which we can eat which kill other animals.
CHOCOLATE! do not feed chocolate to your dog.
Think of yourself as a factory.
Factories are not interchangeable. You can't just go to a textile processing factory, throw a ton of soybeans onto the conveyor belt and expect that you'll get soybean oil out of them. If you try, it's just going to gum up the works and screw everything up.
Now, animals are much closer to each other in makeup than soybean and textile factories. It's more like we're all cotton processing plants - but there are still significant differences. If you try to process dyes in a factory that isn't equipped to handle it, you'll still get a mess.
So it is with animals. We have some similarities, most animals can process what most other animals can to some extent, but there are still significant differences.
Why are some berries poisonous? - Biology
Short Answer, Yes. Plants That Poison by Schmutz and Hamilton states that the poisonous parts on hollies are the berries. "The berries of all species are reported to be poisonous if eaten in quantity. The toxic principle is ilicin. Although not considered very poisonous, the attractive red or black berries should be considered dangerous to small children [and animals]." Symptoms listed are "nausea, vomiting, diarrhea and stupor due to depression of the central nervous system." They also note, "These are the hollies used extensively as Christmas decorations. Indians and early settlers used the leaves to make a mild brew such as 'yaupon tea'."
Recently I have had phone calls from Extension agents and Green Industry professionals in 3 states asking about "poisonous" hollies in the landscape. I am not sure what stimulated this sudden interest but will share what I learned. Please remember, I am neither a pharmacologist nor a toxicologist and I certainly have done no human feeding or dose response studies. That sort of work seems more appropriate for the medical community than for a horticulturist.
Plants That Poison by Schmutz and Hamilton states that the poisonous parts on hollies are the berries. "The berries of all species are reported to be poisonous if eaten in quantity. The toxic principle is ilicin. Although not considered very poisonous, the attractive red or black berries should be considered dangerous to small children [and animals]." Symptoms listed are "nausea, vomiting, diarrhea and stupor due to depression of the central nervous system." They also note, "These are the hollies used extensively as Christmas decorations. Indians and early settlers used the leaves to make a mild brew such as 'yaupon tea'."
Common Poisonous Plants and Mushrooms of North America by Turner and Szczawinski, gave a more thorough treatment. In the section on English holly (Ilex aquifolium) and related species, they write "Berries and leaves may cause digestive upset berries occasional cause of poisoning in children, but not known to be fatal." They say the berries and leaves contain theobromine, a caffeine-like alkaloid listing the same toxicity symptoms as Shmutz and Hamilton. "However, fatalities from holly are unknown, and their poisonous properties are frequently overstated. Mild doses of the leaves or berries cause stimulation of the central nervous system, whereas higher doses cause depression of the central nervous system." If large quantities of the berries have been ingested, they suggest that vomiting be induced followed by activated charcoal and a saline cathartic, excess stimulation caused by theobromine can be countered with barbiturates and benzodiazipines. Obviously, medical professionals need to be involved if treatment becomes necessary.
When I checked for specific toxicity references to our common landscape hollies, I found almost nothing. For the native evergreen species besides Yaupon holly, Ilex opaca, I. cassine, I. glabra and deciduous species, I. decidua and I. Verticillata, I found that the leaves of I. cassine were sometimes used by Native Americans like the leaves of I. vomitoria to make black drink. There were no other references uncovered that indicated these native species have any toxicity at all.
It seems that rather than panicking if holly berries or leaves are ingested, we should remember that Turner wrote, "Fatalities are unknown and their poisonous properties are frequently overstated." In my search only a few species were listed as having medicinal uses. If your callers cannot watch what their toddlers [or animals] are eating, they probably have much more to fear from common beverages, condiments and household chemicals than from hollies in their landscape.
by Richard E Bir
Taken from Auburn University Website
Awareness and prevention
Awareness and prevention are the best defenses against the accidental ingestion of poisonous berries and seeds. Here are a few steps you can take to help protect your child.
Know the name of the plants growing in and near your home. If possible, write the scientific and common names of the plants on a weather-proof tag and attach it to the plant.
If you&rsquore not sure of this information, take a cutting (a 6- to 8-inch piece that includes leaves, berries and flowers) from the shrub to a garden center, nursery or florist for identification.
If an accidental ingestion does happen, this information will be very helpful to the Poison Control Center.
Check your children's play areas often for growing weeds and remove them before your children find them. Clean up fallen seeds or pods from nearby trees.
For removal of poison ivy, oak or sumac plants, use only commercial herbicides intended for these plants and follow the manufacturers' directions carefully.
Consider using artificial berries for indoor decorations as an alternative to live berries, which may be poisonous.
Why do poisonous berries exist? Didn't berries evolve to be eaten?
Some poisonous berries aren't poisonous to many animals, just humans happen to be one of the unlucky species. Many species of birds can eat a variety of poisonous (to human) berries.
The poison can also acts as a defense for the plant as to not get destroyed by animals when eaten. Berries are a strong source of nutrients for the germinating seeds, although it is true the seeds won't move as far as those excreted by animals.
Berries didn't necessarily evolve to be eaten. Sure some did, but "berry producing plants" is such a massive range of plants that evolved independently under so many different circumstances, it's unwise to assume the purpose of berries is to attract animals to eat them so the seeds can be excreted far away from the mother plant.
Here's an article by the Alaskan Fish and Game department explaining how deer are able to eat plants that are poisonous to humans, closely related to your question. http://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=249
And Slater Museum of Natural History on birds eating poisonous berries http://slatermuseum.blogspot.com/2009/09/why-poisonous-fruits.html
If you had a specific plant you were wondering about, there might be some research already done as to why the plant likely evolved the way it did.
I didn't mean to personify evolution as some sort of "choice" the plant has made. I am fully aware Evolution isn't some planned design or conscious choice the thing takes. I just felt the word choice made my post flow a bit faster without being bogged down with explicit wording regarding the workings of evolution.
Sort of a "Eh, they'll get what I mean." moment.
Interestingly, birds also can't taste spicy peppers, which leads to the idea that the peppers evolved to be eaten by birds and be carried around much farther than other animals would.
Could it be possible that there may be poisonous ones that evolved to be more so in order to take advantage of the dead/decaying animal that ate the berry?
Berries didn't necessarily evolve to be eaten.
The very phrasing, "to be eaten," is a subtle but important misunderstanding of evolution.
It is more accurate to say that, "berries that are eaten (and whose seeds survive digestion) tend to be spread more/faster."
Evolution is not an actor, it doesn't choose or design, it is a random process with a non-random selection method. Things survive or they don't. Also, some traits which decrease odds of survival are linked to traits which increase odds of survival. Those relationships are often opaque.
Developing plant embryos don't get their nutrients from the fleshy parts of berries. The energy the seedling needs to grow until it can start to photosynthesize on its own is stored in the cotyledon(s).
I'm confused about this statement
Berries didn't necessarily evolve to be eaten. Sure some did, but "berry producing plants" is such a massive range of plants that evolved independently under so many different circumstances, it's unwise to assume the purpose of berries is to attract animals to eat them so the seeds can be excreted far away from the mother plant.
Could you explain your reasoning more thoroughly?
But--seeds are packed with nutrients. So why would the berry evolve if not because some animal ate it and spread the seed with it.
I wonder how important deer are to poisonous plants since they tend to be the immune to most of them and actually prefer some, like poison ivy.
Seems like being poisonous to large animals like mammals that snap branches and strip leaves, but not to birds that can carry seeds afar, would be really good for survival.
The poison can also acts as a defense for the plant as to not get destroyed by animals when eaten.
I don't believe this. I can understand a foul-tasting berry or thorns repelling animals and therefore protecting the plant, but poison is likely to just kill them without the animals knowing what killed them.
For one, the animal won't understand why it's sick an hour after eating a bunch of food, and also if the animal dies it's not going to pass any genes onto offspring.
This is well said. Iɽ just like to add a quibble with OP's wording: berries did not evolve to do anything. Evolution is not really purpose-driven. There is no end-game. There is no final level. It is a process. In the words of Richard Dawkins, evolution has "no higher purpose than to perpetuate the survival of DNA." Now, I see OP was not suggesting that the berries had a goal in mind and then decided to evolve that trait. Hell, I have been guilty of doing the same thing. But we (especially me, as a biologist) need to be careful and accurate with our wording. It will go a long way in battling evolution deniers (no more, "Why do men have nipples?" arguments).
Regarding evolution and choice, or purpose, unfortunately the terminology creeps in to writing and discussion of natural seletion all over the place. Watch any good-quality animal documentary, even a BBC or National Geographic one, and there will usually be statements like 'the tortoise shell exists to provide protection', 'the purpose of the stripes is to provide camouflage', when in fact it should be 'tortoises which have thicker shells survive better than those which don't, and pass the tendency on', or likewise with better camouflage.
The trouble is, I feel that while we who know about natural selection can understand what is meant, there are people who haven't 'got' Natural Selection, or who are creationists, who are puzzled by them. A creationist is of course reinforced by the idea that eyes appeared to see, even without knowing that there was light, or that animals spontaneously develop patterns similar to their environment in order to improve their camo.
It's best to be rigorous in our terminology.
Some poisonous berries aren't poisonous to many animals, just humans happen to be one of the unlucky species.
And the flip side is also true: many things that aren't poisonous to humans are to other animals. We've no complete list, but for something like dogs, which have lived alongside humans, we know of some foods that humans can eat with no trouble that will do a serious number on the other animal:
Birds, rabbits, and some large animals, including horses, are especially sensitive to avocados, as they can have respiratory distress, congestion, fluid accumulation around the heart, and even death from consuming avocado.
Chocolate intoxication is most commonly seen around certain holidays—like Easter, Christmas, Halloween and Valentine’s Day—but it can happen any time dogs have access to products that contain chocolate, such as chocolate candy, cookies, brownies, chocolate baking goods, cocoa powder and cocoa shell-based mulches. The compounds in chocolate that cause toxicosis are caffeine and theobromine, which belong to a group of chemicals called methylxanthines. The rule of thumb with chocolate is “the darker it is, the more dangerous it is.” White chocolate has very few methylxanthines and is of low toxicity. Dark baker’s chocolate has very high levels of methylxanthines, and plain, dry unsweetened cocoa powder contains the most concentrated levels of methylxanthines. Depending on the type and amount of chocolate ingested, the signs seen can range from vomiting, increased thirst, abdominal discomfort and restlessness to severe agitation, muscle tremors, irregular heart rhythm, high body temperature, seizures and death.
Dogs are far more sensitive to ethanol than humans are. Even ingesting a small amount of a product containing alcohol can cause significant intoxication. Dogs may be exposed to alcohol through drinking alcoholic drinks, such as beer, wine or mixed drinks (those with milk, like White Russians and “fortified” egg nog, are especially appealing to dogs), alcohol-containing elixirs and syrups, and raw yeast bread dough (please see the above section on bread dough). Alcohol intoxication commonly causes vomiting, loss of coordination, disorientation and stupor. In severe cases, coma, seizures and death may occur.
Grapes and raisins have recently been associated with the development of kidney failure in dogs. At this time, the exact cause of the kidney failure isn’t clear, nor is it clear why some dogs can eat these fruits without harm, while others develop life-threatening problems after eating even a few grapes or raisins. Some dogs eat these fruits and experience no ill effects—but then eat them later on and become very ill. Until the cause of the toxicosis is better identified, the safest course of action is to avoid feeding grapes or raisins to your dog. Dogs experiencing grape or raisin toxicosis usually develop vomiting, lethargy or diarrhea within 12 hours of ingestion. As signs progress, dogs become increasingly lethargic and dehydrated, refuse to eat and may show a transient increase in urination followed by decreased or absent urination in later stages. Death due to kidney failure may occur within three to four days, or long-term kidney disease may persist in dogs who survive the acute intoxication.
All close members of the onion family (shallots, onions, garlic, scallions, etc.) contain compounds that can damage dogs’ red blood cells if ingested in sufficient quantities. A rule of thumb is “the stronger it is, the more toxic it is.” Garlic tends to be more toxic than onions, on an ounce-for-ounce basis. While it’s uncommon for dogs to eat enough raw onions and garlic to cause serious problems, exposure to concentrated forms of onion or garlic, such as dehydrated onions, onion soup mix or garlic powder, may put dogs at risk of toxicosis. The damage to the red blood cells caused by onions and garlic generally doesn’t become apparent until three to five days after a dog eats these vegetables. Affected dogs may seem weak or reluctant to move, or they may appear to tire easily after mild exercise. Their urine may be orange-tinged to dark red in color. These dogs should be examined by a veterinarian immediately. In severe cases, blood transfusions may be needed.
Are Hawthorn Berries Poisonous?
On the contrary. Hawthorn berries are one of natures many natural remedies which have been in use through the ages, and now is commercially marketed for its benefits to the heart, blood pressure and the cardio vascular system in general. It is found in the northern hemisphere and more commonly in the Mediterranean region.
The tree itself was regarded as sacred by Christians, as it was supposed to be these thorns whose crown Christ had worn. Earlier still Celts in England used it for inscribing runes. Medicinally it was used by the same Celts to remedy the broken heart, by western herbal lore as benefiting the cardiovascular system and by the Chinese as an aid to digestion. Its use is yet more common in Europe, where there has been clinical research on its benefits to the circulatory system. Chemicals in the berries help the heart muscles in better enzyme metabolism and oxygen utilization. Its berries are used as combinations, tinctures and in herbal teas.
Hawthorn berries are said to contain vitamins C and B complex, crataegin, carotene, flavonoids and sugars. The flowers are important for nectar eating insects and the tree is known to be recommended in areas where water conservation is being pursued.