Theme B: B4 Ecosystems - B4.2 Ecological Niches

Question 1

definition + what it includes

Ecological Niche

Answer 1

the unique role a species plays in an ecosystem. it includes where the organism lives (spatial habitat) and its role in nature: what and how it eats (feeding activities) and its interactions with other species.

Question 2

What niche an organism can fill depends on…

Answer 2

1) How it obtains food (specialisation reduces competition)
2) Zones of tolerance (range determines habitat)
3) how it interacts with other species in th ecosystem

Question 3

obligate aerobes

Answer 3

require oxygen and cannot convert food nutrients into energy without it. Obligate (no choice) and aerobic (oxygen).

if oxygen in their environment is greatly reduced (hypoxia) or absent (anoxia) they could die.

Question 4

obligate anaerobes

Answer 4

Single-celled organisms that have no tolerance to the presence of oxygen and are poisoned by it. obligate (no choice) and anaerobes (no oxgen).

prokaryotes present on Earth for the first billion years of life were intolerant of oxygen, which was not a problem until photosynthesis evolved and that oxygen started to collect in the atmosphere and water.

today to excape Earth’s atmosphere, obligate anaerobes live in places where air cannot reach them such as in soil, deep water, or intestines of animals/humans. e.g. bacteria that causes tetanus and methanogenic archae.

Question 5

facultative anaerobes

Answer 5

Capapble of carrying out both anaerobic and aerobic respiration. facultative (choice) and anaerobes (no oxygen).

e.g. E. coli and yeast. baker’s yeast, a single-celled fungus, can switch to anaerobic respiration when oxygen is not present: they are neither hurt by nor killed by the presence of oxygen.

Question 6

what 3 groups of organisms use photosynthesis as their mode of nutrition?

Answer 6

3 groups of photosynthetic organisms
1) plants
2) algae
3) some bacteria

some cell biologists might call them autotrophs as they produce their own food, some ecologists might call them primary producers in terms of the role they place in an ecosystem

Question 7

heterotrophs

Answer 7

organisms that must eat they’re food, they are consumers not producers. e.g. zooplankton, sheep, fish, birds.

there are different types of heterotrophs depending on how they get their nutrients.

Question 8

holozoic nutrition

Answer 8

organisms that obtain their food this way are called consumers. whole pieces of food are eaten and digested internally. most heterotrophs do this.
1) ingestion = eating something
2) digestion = chemical breakdown into smaller molecules
3) absorption = blood stream absorbs some of the smaller molecules
4) assimiliation = becoming part of the cells and tissues, hence the smaller molecules are used by our cells
5) egestion = the left over molecules that cannot be absorbed pass out of the anus as waste

Question 9

mixotrophic

Answer 9

organisms that are both autotrophic and heterotrophic, hance that can make their own food and ingest nutrients from other organisms. So they are consuming things as well as producing their own food.

e.g. the genus Euglena is made up of species that are single-celled protists with photosynthetic pigments but also can ingest food from the water around it.

obligate mixotrophs must use both methods.

facultative mixotrophs can use one method or the other depending on what is available in the environment. e.g euglena

Question 10

sapotrophs

Answer 10

organisms that live on or in non-living organic matter, secreting digestive enzymes and then absorbing the products of digestion. they lay an important role in the decay of dead organic materials.

sapotrophic decomposers: digest matter externally. they release enzymes onto their food and the digestion happend outside their body, they then absorb the digested nutrients. e.g. some fungi and bacteria can spray diegstive enzymes onto things.

Question 11

what are the 3 ways in which archaea get energy/nutrition (ATP)

Answer 11

1) heterotrophic nutrition (from other organisms)
2) photosynthesis (absorbing light energy)
3) chemosynthesis (oxidising inorganic chemicals without help of sunlight)

Question 12

dentition

Answer 12

relates to teeth. one of the more visible adaptations of animals are ones that relate to their diet. what can organism eats says a lot about its place in an ecosystem. it can help us determine which spcecies occupy which niches, hence working out what extinct species ate can help us work out what niches they occupied. palaeontologists often look at teeth and jawbones - much better preserved in the fossil record than soft digestive organs for example.

Question 13

examples of extant and extinct species

hominidae

Answer 13

we are primate and belong to the family hominidae or the great apes. it includes the following genera (singular genus):
* pongo, orangutans (there are three extant (living) species)
* gorilla, two extant species
* pan, chimpanzees, two extant species
* homo, one extant species, modern humans

dozens of species in the family hominidae are now extinct, so the only evdience we have of their presence on Earth is their fossil remains (bones, skulls, teeth, sometimes fossil DNA)

extinct species include
* australopithecus africanus
* homo erectus
* paranthropus robustus
* homo floresiensis
* Homo neanderthalensis

Question 14

adaptations of herbivores that allow them to eat plants

Answer 14

Plant leaves tend to be protected by thick layers of cells with semi-rigid cell walls, and not many organisms possess the enzymes necessary to break down cellulose.
* Aphids: Use stylets to pierce plants and drink sugar-rich sap.
* Grasshoppers & caterpillars: Use sharp mandibles to cut and chew leaves; often considered crop pests.
* Cows & sheep (herbivorous vertebrates): Have broad, flat back teeth for grinding plants.
* Ruminants (e.g., cows): Regurgitate and re-chew food (chewing the cud) to aid digestion.
* Microbial help: Gut bacteria and archaea assist in breaking down cellulose.
* Giraffes: Long necks and legs help them reach high leaves; tough tongues withstand acacia thorns.

Question 15

adaptations of plants for resisting herbivory

Answer 15

• thick bark
• spines/spikes
• stinging parts
• phytotoxins (made from secondary compounds, molecules that are not necesarry for the normal growth or reproduction of the organims but can be used as a toxin for defense (e.g. penicillin, caffeine, foxgloves))

Question 16

adaptations of animals to neutralise toxins

Answer 16

• Some herbivores (e.g. ruminants and insects) rely on gut microbes that can detoxify plant chemicals like alkaloids and tannins.
• Microbial colonies increase when small amounts of toxic plants are eaten, improving tolerance over time—but only up to a point.
• Cautious sampling helps animals avoid poisoning by testing small amounts of new plants first.
• Moose saliva contains proteins that neutralize tannins.
• Toxins that enter the bloodstream are sent to the liver, where they are broken down and neutralized.

Question 17

chemical adaptations of predators for catching prey

Answer 17

• venom (black mamba in southern and eastern parts of africa) contains neurotoxins that paralyse its prey. after buting the bird/rodent and it no longer mves, they ingest it whole.
• pheremones, organic molecules ued to send message through the air and some to attract males. certain species of orb-weaver spiders can produce chemicals that mimic sex pheromones of moths.

Question 18

physical adaptations of predators for catching prey

Answer 18

To find prey:
* birds of brey like hawks and eagles have excellent eyesite, owls have eyes that are adapted for seeing in low light at night.
* bats and dolphins use echolocation, involves sending out ultrasonic vibrations, and their brains process how waves bounce off objects like prey in the environment (percieving their environment with sound).
* sharks have adapted organs in their head called ampullae of lorenzini which detect changes in electromagnetic fields allowing them to detect prey. as fish or seals swim, its nervous system releases small discharges of electricity.

To catch prey:
* fly, run, swuim, rapidly and with precision to chase down prey
* claws, beaks, teeth, and well adapted digestive system to kill prey and extract nutrients
* brain that quickly assesses rapidly changing circumstances and make complex decisions involving the time, energy, and risk involved in pursuing prey. if the risk of exhaution or injury is too great, predator must know when to give up and try again later

Question 19

behavioural adaptations of predators for catching prey

Answer 19

Ambush predators
* hide and wait for prey and then pounce on them
* anglerfish such as frogfish hide on the ocean floor and use a lure called illicium (a long thin appendage protruding from their head) to attract prey. open their mouts in a fraction of a second to engulf the prey before the prey even known they’re there

pack hunting
* common in wolf species, makes chances of bringing down a large animal greater if several wolves work together, this requires an established relationship of trust (they know who the leader is and which are subservient).

pursuit predator
* relies on speed to outrun prey
* cheetahs, fastest land mammal at least over short distances, and are well adapted to chase down gazelles.
* speed is not the only strategy, endurance can work sometimes too. the idea is then to pursue prey for many hours until it drops from fatigue. known as persistence hunting. humans living as hunter gathers use this.

Question 20

chemical adaptations of prey for resisting predation

Answer 20

prey can produce chemicals to dissuade or fool predators, or produce chmicals that taste bas or posion the predator
* on ehighly poisonous dart frog, produces an alkalid on its skin that can interfere with muscle function, inclduing heart muscles, causing death.

Question 21

physical adaptations of prey for resisting predation

Answer 21

camoflauge is the ability of an ogranism to take on the appearance of its surroudings can work well against predators that rely on vision.
* some orgas only have one fixed adaptation, such as coloration patterns on wings of moths
* others can adapt to their environment, like certain species of octupus that modify their skin cells to adapt to the colours of their environment, and they can generate bumpy or smooth textures to mimic the surface they hide on

aposematism
* using dramatically bright an dunusual colours (yellow, blue and red) to inform predators that they are poisonous, like poision dart frogs.
* other prey mimic these warnings, like the non-venemous kingsnake that look like coral snakes who are poisonous.

warning vocalisations
* deter predators and warn fellow prey ther eis danger. jays, blackbirds, and non-human primates like monkeys use this

Question 22

behavioural adaptations of prey for resisting predation

Answer 22

Many animal behaviours are instinctive and encoded in their DNA. These can include fleeing at the sight of a predator, hiding, forming groups or using certain types of dissuasive behaviour to ward off predators.

The expression “there is safety in numbers” is not just a figure of speech. A large group attacked by a predator will suffer fewer kills than solitary individuals or small groups that are attacked.
e.g. when threatened, a herd of elephants will group together, with the largest adults placing themselves facing outwards and the young positioned in the centre. Predators will often be dissuaded from attacking a group because the risk of getting injured is greater than the chance of successfully taking down a vulnerable, solitary, juvenile, for example.

Question 23

how does the rate of development differ between the 3 types of adaptation?

Answer 23

behavioural is the fastest, then physical, and then chemical adaptations develop the slowest.

Question 24

adaptations of plants for harvesting light

trees

Answer 24

trees grow very tall so the light is not blocked by other pants. sturdy woody trunks allow them to dominate the canopy. building a sturdy trunk and strong supporting branches needs a lot of energy and nutrients.

Question 25

# adaptations of plants for harvesting light lianas

Answer 25

**lianas** (vines) grow through other tress and use them as support. they take root on the forest floor and use trees as a scaffold to grow into the canopy. liana seedlings do the opposite of normal seedlings: they grow towards shade or towards tree trunks and the start to climb.

Question 26

# adaptations of plants for harvesting light lianas epiphytes

Answer 26

**epiphytes** (air plants) grow on tree trunks where there is more light (canopy of understorey) e.g. orchids. their roots are not in the soil on forest floor. they are attatched to tree trunks and get moisture from water trickling along branch when rains or humidity in air. they are well adapted to survive on very little water (best way to kill an orchid is to overwater it). * some parasitic pants like strangler figs (**hemi-epiphytes**) climb up the trunk and eventually outcompete the tree (their host) for light, which kills the host.

Question 27

# adaptations of plants for harvesting light lianas growing in the shade (shade tolerant shrubs)

Answer 27

shade-tolerant shrubs grow on the forest floor where low levels of light are within their range of tolerance. they are well adapted to absorbing the wavelengths of diffuse sunlight that remain after passing through other leaves, notably the longer wavelengths in the red part of the spectrum. e.g. bananas and ginger are from herbaceous plants that grow in the understorey of forests in the tropics. Herbaceous plants, otherwise called herbs, are those that do not produce a woody stem with bark the way trees do. Banana plants are herbs because the part that looks like a woody stem is, in fact, not made of wood but of rigid layers of the bases of the leaves. Other examples of herbaceous plants that can grow on the forest floor are wildflowers and berries such as strawberries.

Question 28

fundamental niche

Answer 28

the potential niche of a species that it could inhabit given its adaptations and tolerance limit. The range of tolerance of all of the abiotic factors for a species. This also includes parts of the niche where other species are more suited to the range of tolerance are likely to outcompete the organism and eat away at its role in its environment. * a very optimistic outlook, showing all the places that an organism **could** live.

Question 29

realised niche

Answer 29

the actual niche that a species occupies because part of its range of tolerance is occupied by competitors. more reaslitic outlook. its the fundamental niche minus all of the areas where that organism gets outcompeted by other species. its smaller than the fundamental niche.

Question 30

competitive exclusion and the uniqueness of cological niches

Answer 30

one species will outcompete the other if their fundamental niches overlap. The species that outcompetes the other will be able to occupy its **entire fundamental** niche, whereas the outcompeted species will have a smaller **realised** niche. this leads to exclusion in parts of the range of tolerance. if a species is outcompeted in **all parts** of its **fundamental** niche, it will be excluded from the **entire ecosystem**. every organism must have a **realised** niche to exist in an ecosystem. this has happened with climate change in particular, as it changes the range of tolerance by introducing different abiotic factors to ecosystems can possibly affect organisms whose niches aren't overlapping yet but will be soon.

Question 31

principle of competitive exclusion

Answer 31

this principle states that no two species in a community can occupy the same niche. if they do coexist for a certain time period, the number os both populations will tend to decrease. In the long run, it is often the case that one species will replace the other - easier to see in microbial populations which reproduce at a very fast rate.

Question 32

interspecific competition (origin of competitive exclusion principle)

Answer 32

the competitive exclusion principle was demonstrated in 1934 by a Russian ecologist (G. F. Gause). her performed a labratory experiment with 2 species of Paramecium: P. aurelia and P. caudatum. His experiment showed the effects of interspecific competition between two closely related organisms (interspecific means two or more different species). When each species was grown in a separate culture, with the addition of bacteria for food, they did equally well. When the two were cultured together, with a constant food supply, P. aurelia out-competed P. caudatum. The experiment supported Gause's hypothesis of competitive exclusion. When two species have a similar need for the same resources in the same space at the same time, one will be excluded. One species will die out in that ecosystem and the other will survive. Paramecium aurelia must have had a slight advantage that allowed it to out-compete P. caudatum.

Question 33

spatial habitat

Answer 33

the physical area inhabited by any particular organism. composed of abiotic and biotic fatcors.

Question 34

tolerance

Answer 34

how well a species reacts to the presence of somthing in its environment.

Question 35

examples of abiotic fatcors

Answer 35

. sunlight, soil type, pH, temp, sand, water

Question 36

examples of biotic fatcors + interactions

Answer 36

biotic interactions can include feeding relationships, provision of shelter such as nest sites, or presence of parasite within the environment.

Question 37

aerobic respiration

Answer 37

chemical transformation of food nutrients intro energy that requires oxygen

Question 38

anaerobic respiration

Answer 38

chemical tranformation of food into energy that does not require oxygen.

Question 39

detritivores

Answer 39

decomposers that digest matter **internally**. they feed on dead, particulate, organic material (mainly plant matter). this waste is also called detritus.

Question 40

chemoautotroph

Answer 40

organism capable of producing its own food using chemical reaction without the need for sunlight. this way of generating energy is called chemosynthesis.

Question 41

tooth anatomy

Answer 41

**incisors**: found at the **front** of your mouth. cut off **bite-sized pieces** of food, acting like scissors. primates that eat mostly plant material (leaf eaters **folivores** and fruit eaters **frugivores**) tend to have **large** incisors. herbivores also tend to have bigger incisors than carnivores. **canines**: to the side of the incisors. **sharper** and used for ripping and tearing tougher materials such as **meat**. **premolars** in the **middle** of your mouth. used for **crushing** or slicing up food. follwed finally by **molars** at the **back**. for **grinding** food and reducing it to a paste before swallowing. generally, the **narrower** and **more serrated** (pointed) the crowns (tops) of the premolars and molars are, the better adapted they are for eating **meat**, whereas the more **rounded** or **blunt** they are, the better adapted they are for eating **plant** material.

Question 42

# diets of extant great apes orangutan

Answer 42

orangutans eat mostly fruit, which explains why they live in trees and occasionally also eat leaves. Some orangutans supplement their diet with insects, eggs or honey, so they can be considered omnivores, but they are essentially frugivores.

Question 43

# diets of extant great apes gorillas

Answer 43

Gorillas eat almost exclusively plant material: leaves, roots and stems. Some occasionally eat ants or termites, but gorillas are herbivores and more specifically folivores.

Question 44

# diets of extant great apes chimpanzees

Answer 44

Chimpanzees are omnivores, preferring fruit but also eating leaves and stems from plants, as well as meat. Chimpanzees consume invertebrates such as ants, termites and bees (and their honey), but also vertebrates such as monkeys, birds (and their eggs), antelope and warthogs, especially the young, which are easier to catch.

Question 45

# diets of extant great apes humans

Answer 45

Humans are also omnivores, eating fruit and grains, but consume vertebrates such as birds, fish, pigs and cattle as well.

Question 46

# connetcing dentition with diet herbivores

Answer 46

If we look at herbivores in general, they tend to have large incisors and wide premolars and molars that have rounded peaks and valleys for shearing and crushing plant material.

Question 47

# connecting dentition with diet carnivores

Answer 47

Carnivores tend to have sharp, pointy teeth, not just their incisors and canines, but even their premolars and molars can be serrated and narrow rather than wide and rounded.

Question 48

# connecting dentition with diet omnivores

Answer 48

Omnivores' teeth are somewhere in between. Their canines are not as long and pointed as carnivores. Their molars are of an intermediate width, not as wide as herbivores but not as narrow as carnivores. Their premolars and molars are usually rounded rather than serrated.

Question 49

complications where dentition doesn't always match diet

Answer 49

dentition matches chimp diet: smaller incisors and long pounted canines for eating meat. orangutans have long pointed canines and yet they do not eat meat, the complication is that teeth are not only for eating, some animals use sharp teeth to intimidate rivals or fend off intruders. gorillas are herbivores but they have very intimidating canines. even though meat plays a big role in many people's diet, our canines, premolars, and molar are not shaped like carnivore teeth.

Question 50

microwear

Answer 50

small abrasions or removal of a tooth's surface, made as organisms chew, whcih can reveal the type of food they were eating. softer foods will leave different marks compared to harder foods, and foods that have grit in them from soil will scratch teeth in a particular way that can be seen and analysed under a microscope.

Question 51

names of forest parts

Answer 51

The **canopy** is the upper layer of a forest where the crowns (tops) of trees are found; zones below the canopy are called the **understorey**, where shorter trees can be found. The **shrub layer** contains the shortest trees and shrubs, while the **forest floor** is home to smaller, non-woody plants. In a dense forest, every square centimetre of the forest floor is almost always in shade, because leaves from plants at every level above it absorb the sunlight and shield the zones below.