3.5 Symbiosis

Question 1

What is co-evolution?

Answer 1

some organisms depend on other organisms because they form a partnership leading to co-evolution
this means that they evolve together over millions of years and the evolutionary change of one organism is triggered by its interaction with the other

Question 2

how are symbiotic relationships formed?

Answer 2

through coevolution

Question 3

What is symbiosis?

Answer 3

symbiosis means ‘living together’ and refers to an intimate relationship between organisms from two

Question 4

what are the different types of symbiosis?

Answer 4

paratism

mutualism

Question 5

REMEMBER!

Answer 5

other living things are an important feature of an organisms ecosystem because organisms depend on one another for food or a habitat for example

Question 6

what is a parasite?

Answer 6

a parasite lives in or on the body of another organism, which is known as the host, and gains energy or nutrients from it
the parasite gains from the relationship and the host is harmed due to loss of valuable resources

Question 7

what are ectoparasites?

Answer 7

parasites such as ticks, fleas, leeches and lice live on the surface of the hosts body and are called ectoparasites

Question 8

what are endoparasites?

Answer 8

parasites such as tapeworms, roundworms, flukes, bacteria and viruses live inside the body of the host and are called endoparasites

Question 9

Why can the majority of parasites not survive in the absence of a host and what are they called?

Answer 9

since they are adapted to live in or on a host, they may have lost some of the organs needed to survive on their own. these are called obligate parasites

Question 10

TOPTIP

Answer 10

parasites fall into two main groups:
obligate parasites need a host to survive
facultative parasites are able to survive outside a host

Question 11

What are tapeworms?

Answer 11

tapeworms attach themselves to the sides of the intestines of animals and obtain partially digested food from their hosts

Question 12

what are fleas?

Answer 12

fleas bite the skin of their host and gain energy by sucking their blood
many types of parasites carry and transmit disease in this way

Question 13

How can parasites be transmitted from one host to another?

Answer 13

direct contact
via resistant stages
via a vector

Question 14

Explain transmission by direct contact?

Answer 14

this is when a parasite is passed directly from one host to another when two hosts come into close physical contact with each other
head lice can only move from one human head to another by direct contact

Question 15

Explain transmission by resistant stages?

Answer 15

some parasites, for example, protozoa, have resistant or resting stage (cysts or oocysts) which can resist drying out and other stresses such as temperature extremes and harsh chemicals
they can survive without a host for a period of time

Question 16

What is a vector?

Answer 16

a vector is an intermediate organism that transfers a parasite from one host to the next
e.g. a species of mosquito which transfers the protozoan parasite plasmodium which causes malaria, from one human host to another

Question 17

What is a secondary host?

Answer 17

a secondary or intermediate host is necessary for some parasites to complete their lifecycle
asexual reproduction or the development of larval stages of the parasite may occur in the secondary host
humans are the secondary hosts for malarial parasites

Question 18

What is mutualism?

Answer 18

both species within a mutualistic relationship benefit in terms of food and energy and are usually compatible in terms of physical structures due to the process of co-evolution

Question 19

Example 1 Herbivores

Answer 19

herbivores must get their energy from the plant material which they eat
however, their digestive systems do not produce cellulase, the enzyme necessary to digest cellulose in plant cell walls
they need the help of cellulose digesting bacteria and protozoa which live in their digestive system
In return these microorganisms get food from the gut of the herbivores

Question 20

Example 2 Coral Polyps

Answer 20

coral polyps are animals and they form a mutualistic relationship with zooanthellae algae which live within the polyp cells
coral providers the algae with carbon dioxide for photosynthesis and other wastes including water and ammonium compounds
they algae provide the coral with sugar and oxygen

Question 21

Explain coral bleaching?

Answer 21

Rising sea temperatures, perhaps due to global warming, causes the loss of the unicellular, symbiotic zooanthelle from coral species.
the coral dies and turns white-coral bleaching

Question 22

Example 3 Clownfish and sea anemones?

Answer 22

clown fish live among the stinging tentacles of sea anemones.
a thick mucus layer on the skin protects the fish from stings, which deter predators
the sea anemone is protected as the presence of the clownfish deters the butterflyfish which eat sea anemones

Question 23

Example 4 Oxpecker bird?

Answer 23

the oxpecker bird feeds on the small insects in the coat of a buffalo
the buffalo benefits from having pests removed while the oxpecker bird exploits a plentiful food source of food

Question 24

Example 5 Lichens?

Answer 24

lichens are a product of a mutualistic relationship between an algae and a fungus which grow together in one unified structure
algae receive nutrients from the fungus in turn receives glucose from the photosynthetic algae

Question 25

What is the evolution of mitochondria and chloroplasts?

Answer 25

It is thought that mitochondria and chloroplasts in eukaryotes evolved from free living bacteria (prokaryotes) which were engulfed by other cells, forming a mutualistic relationship

Question 26

DONT FORGET

Answer 26

prokaryotes do not have membrane bound organelles such as a nucleus, chloroplasts or mitochondria
plant, animal and yeast cells are all eukaryotes and have a membrane-bound nucleus and other membrane-bound organelles such as mitochondria and chloroplasts