Ecology Flashcards
(126 cards)
1
Q
Define ecology
A
The study of the relationship of living organisms with each other, and the environment
2
Q
Define population
A
A group of organisms of the same species occupying the same area at a given time
3
Q
Define community
A
A group of organisms of different species living in a given area at a given time
4
Q
What is an ecosystem?
A
A biological unit consisting of biotic and abiotic factors interacting with each other
5
Q
What is a biosphere?
A
Any part of the earth occupied by living things
(Divided into aquatic and terrestrial)
6
Q
What is a biome?
A
A region of the biosphere with a definite climate and organisms
7
Q
What is a habitat?
A
A specific locality in the biome where an organism lives
8
Q
Define the term ‘biological niche’
A
This is the role and position that a species has within its habitat
9
Q
Distinguish between realized niche and fundamental niche
A
Realized niche is the actual space an organism inhabits and the resources it can access as a result of limiting pressure from other species.
- It occurs in the presence of predators, competitors and parasites; limiting their habitat and roles performed by an organism (it is smaller in size)
While fundamental niche is the entire set of conditions under which animal can survive and reproduce itself
- It occurs in the absence of predators, competitors and parasites, allowing an organism experience, a larger habitat, and perform a variety of roles
10
Q
Define abiotic factors
A
These are nonliving factors in an ecosystem or environment
11
Q
What are biotic factors?
A
These are the living things in an ecosystem
12
Q
What are producers?
A
These are organisms that can synthesize their own food
13
Q
Define Consumers
A
These are animals that feed on plants or other animals
14
Q
Consumers that feed exclusively on plants are called?
A
Primary consumers or herbivores
15
Q
Consumers that feed on herbivores are called?
A
Secondary consumers
16
Q
Consumers that feed on
both primary and secondary consumers are called?
A
Tertiary consumers
17
Q
What are decomposers?
A
These are organisms that feed on dead organic matter (DOM)
18
Q
What is the difference between detritivores and decomposers.
A
Detritivores are usually macro organisms, and start the decomposition process
Decomposers are micro organisms that complete the process of decomposition
19
Q
What is the importance of consumers?
A
- They regulate population of plants
- They release carbon dioxide gas, which plants use to make their own food
- Decomposition of dead consumers provides nutrients to the soil
- Lower consumers provide food to higher consumers
- They regulate the population of other animals
20
Q
What is the importance of decomposers?
A
- They recycle nutrients by feeding on DOM
- Some decomposers like mushrooms, are a source of food to some animals
- They provide carbon dioxide to green plants
- They unlock the trapped energy in the body of dead organisms
21
Q
What is the principal source of energy?
A
The sun
22
Q
Why do autotrophs only trap about 1% of the total energy available from the sun?
A
- Part of the light cannot be used or captured by their pigments
- Sunlight energy is trapped by the ozone layer
- Some energy is converted into heat before reaching the plants
- Some energy is reflected by dust, particles, clouds, surfaces, vegetation, water, etc
- Some energy is used in evaporation and transpiration
23
Q
What is primary productivity?
A
This is the amount of energy and organic matter stored in primary producers per unit area per unit time
24
Q
What factors affect primary productivity?
A
- Temperature
- carbon dioxide
- Light intensity
- Amount of water available
25
Define a food chain
This is a linear flow of energy from one trophic level to another
26
What is a food web?
A complex nutritional interrelationship that illustrates alternative food sources, and predators for each organism
27
What is an ecological pyramid?
These are histograms that provide information about feeding levels in Ecosystems
28
What is the pyramid of numbers?
This is a histogram, representing the number of different organisms at each trophic level in an ecosystem at any one time
29
Give the limitations of the pyramid of numbers
-Drawing the pyramid, accurately to scale may be difficult
- The pyramid may be inverted
- The tropic level of an organism may be difficult to ascertain
- The young forms of species may have a different diet from adults
30
What is the pyramid of Biomass?
This is a histogram showing the total dry mass of organisms present at each feeding level
31
Give disadvantages of the pyramid of biomass
- Does not account for the rate of production
- It may also be inverted
32
What is the pyramid of energy flow?
It is a histogram showing the total amount of energy present at each feeding level
33
Give the advantages of the pyramid of energy flow
- It can never be inverted
- It accounts for the rate of production
- Allows comparison of ecosystems
34
What are the disadvantages of pyramids of energy?
-Difficult to obtain data.
-The organisms are killed.
35
What are the general problems of ecological pyramids?
- They may not always indicate the actual trophic level
-They always omit decomposers
- Not every part of the organism is edible
36
Define trophic efficiency
This is the percentage of energy at one trophic level that is converted into organic substances at the next trophic level.
37
Why is the transfer of food from producers to primary consumers the lowest?
- Plants contain cellulose which many animals cannot digest, because they lack cellulase enzyme
- Some energy is lost in respiration
- energy is lost in form of excretion
-Some parts of the plants are indigestible
- some parts are unpalatable
- some parts cannot be accessed eg roots
38
What are the adaptations of herbivores to feeding on plants?
- They chew cud, which increases on the breakdown of plant material.
- Some herbivores have symbiotic bacteria.
-They have very many large, molars and premolars, which increases the surface area for grinding.
- Some have a four chambered stomach increasing on surface area for digestion.
- They have a long elementary canal to increase the surface area for digestion.
39
Why is the Trophic efficiency from primary consumers to secondary consumers higher?
- Animal bodies have a lot of proteins, which are easier to digest by proteases
- The faeces contain much less undigested matter
40
Why is in Trophic efficiency From primary consumers to secondary consumers not still 100%?
- Some energy is lost through respiration
- Some energy is lost through excretion
- Some parts are not edible.
- Some energy is lost through egestion
41
Why doesn’t the length of the food chain exceed five trophic levels?
Because the number of organisms decreases at each successive feeding level, and the energy left in organisms is too little to support the large numbers of consumers
42
What is gross productivity?
This is the total amount of energy and organic matter, stored in an organism over a period of time
43
What is Net productivity?
This is the amount of energy and organic matter, stored in an organism, and passed on to the next trophic level
44
What is gross primary productivity?
This is the total rate at which autotrophs synthesize organic matter per unit area per unit time
45
What is net primary productivity?
This is the amount of energy transferred from primary producers to primary consumers per unit time
46
True or false
Net primary productivity is equal to gross primary productivity minus respiration and metabolism
True
47
What is the nitrogen cycle?
This is the saturation of nitrogen in an ecosystem from one part to another
48
Describe the carbon cycle
- In the nonliving environment, carbon is present as carbon dioxide In the air and dissolved in water; carbonates in rocks and carbon in fossil fuels
FIXATION
- The carbon in fossil fuels, and that in carbonates is not available until it is burnt or chemically changed
- The carbon present in carbon dioxide is the basic source which enters the organism through photosynthesis by plants, and then into various organisms through the food chain
RELEASE BACK INTO THE ENVIRONMENT
- Released as carbon dioxide during respiration in organisms
- By decomposition of dead bodies and body waste by microorganisms.
- By burning of wood and fossil fuel’s.
- By the solution of carbonate rocks.
- By volcanic activity of rocks.
49
What human activities affect the carbon cycle?
- Cutting trees and plants that absorb CO2.
-Burning of fossil fuels.
-Afforestation and reforestation
50
Describe the nitrogen cycle
FIXATION
- The atmosphere has 79% nitrogen but this cannot be taken up by organisms unless fixed
- Nitrogen in soil, reduced to ammonium ions, catalyzed by nitrogen fixing bacteria, which may be free living for example Azotobacter or symbiotic bacteria in root nodules such as Rhizobia bacteria
- Lightning causes atmospheric nitrogen and oxygen to react, and produce oxides of nitrogen which dissolve in rainwater fall to the ground as weakly acidic solutions
- Industrial fixation by chemical fertilizer factories using the Haber process
NITRIFICATION
- Ammonium compounds in the soil are converted first to nitrate ions (highly toxic to plants) by nitrosomonas bacteria, and later to nitrate ions by nitrobacter
AMMONIFICATION/ PUTREFACTION
- Decomposers, such as saprophytic, bacteria and fungi, convert nitrogen, rich organic compounds such as urea into ammonia and ammonium containing salts
ASSIMILATION
- Inorganic ammonia, ammonium, and nitrate ions are absorbed by plant roots to make nucleic acids, amino acids and proteins.
- When animals eat plants, the proteins are converted into animal proteins.
DENITRIFICATION
- Pseudomonas denitrificans convert ammonia and ammonium ions back into nitrates and nitrates ions, then into molecular, nitrogen and oxygen
51
Explain the relationship between a Rhizobium and a legume
- It is a mutualistic relationship in which both organisms benefit.
- The Rhizobium converts nitrogen into nitrogen containing compounds used by the legume for bodybuilding
- The Rhizobium also gives carbon dioxide to the plant which is used in photosynthesis.
-The legume provides the Rhizobium with shelter,
-The legume also provides the Rhizobium food.
52
What is ecological succession?
This is a gradual change in the community composition from a simple community to a stable complex community
53
What are Pioneers?
These are the first sets of organisms to occupy the area
54
What is primary succession?
This is a gradual change from a simple community to a more stable complex community in a newly formed area, where no life previously existed
55
Describe primary succession on land
- Lichens which are the Pioneers attach to an exposed rock surface
- They secrete mild acids that slowly break down the rock, creating cracks on the surface
-They trap wind-blown soil particles forming soil.
- The cracks allow for accumulation of DOM, which leads to soil formation
- They die and decompose to form soil and organic matter
- The soil supports the growth of simple plants such as mosses and ferns, which are called opportunists
- Their roots penetrate and break rocks into soil particles
- Decay of the simple plants increases the nutrients in soil
- After time the soil becomes deep, moist and fertile enough to support the growth of mid successional plants, such as shrubs, grasses.
- Late successional plants mostly trees that tolerate shade, replace the midsuccessional plants and a complex forest community is reached.
56
Define secondary succession
This is a gradual change from simple community to a complex one in an area where life is already present, but has been altered in someway
57
What are the characteristics of the early colonizers of primary succession?
- Species have low biomass
- Species have a short lifespan.
- Species are simple and small sized
-Species diversity is very low.
-Community is open.
- Species may show symbiotic relationships to aid establishment.
- Species are poor competitors and get replaced by higher plans.
- The community has many producers a few decomposers.
- Net productivity is high.
- Feeding relationships are simple.
58
What are the characteristics of the late colonizers of primary succession?
- Plants are of large size and complex.
- Species diversity is high.
- Community is a mixture of producers consumers and decomposers.
- Biomass is high.
- Net productivity is low.
- Community takes a long time to establish.
- Increased soil depth and nutrients.
Interspecific competition is high.
- Little space for new species.
- Feeding relationships are complex.
59
What is population size?
The total number of organisms of a population in a given area at a given time
60
Define population density
This is the total number of organisms of a species per unit area per unit time
61
Define birth rate / natality
This is the number of new individuals produced by one organism per unit time
62
Define death rate / mortality
The number of individuals dying per unit time per unit of population
63
What is population growth?
A change in the number of individuals.
Can be increase (positive) or decrease (negative)
64
What is population growth rate?
The change in number of individuals per unit time
65
Define carrying capacity
The maximum number of individuals of a given species that can be sustained indefinitely in a given area of land
66
What is age structure or distribution?
A description of the abundance of individuals of each age
67
Define biotic potential
The maximum growth rate of a population under ideal conditions with unlimited resources, and without any growth restrictions
68
What is a limiting factor?
These are elements that prevent a population from attaining its biotic potential
69
Define immigration
The movement of individuals into a population from neighboring populations
70
Define emigration
The departure of individuals from a population
71
What is population distribution?
The way organisms are dispersed in a habitat
72
Define survivorship
This is the percentage of an original population that survives to a given age
73
What is the importance of estimating population size?
- Enables monitoring of population growth.
- Enables determination of habitat requirements of the species.
- Enables determination of carrying capacity in the area.
- Enables determination of age structure and sex ratio of a population.
- Enables projection of how population size is likely to change with time.
74
What factors should be considered before counting organisms?
- The nature of the vegetation cover of the habitat.
- Size of organisms under study.
- Facilitation in terms of equipment to be used.
- Behavior of the organism.
- Topography of the area.
- Type of habitat.
- Risks involved during the exercise.
- Seasonal changes and it’s affect on organisms.
75
What are the methods of determining population size of organisms?
1. Direct counting method
2. Aerial photography
76
What are the methods of counting the population by sampling?
1.Capture mark release recapture method
2. Use of a quadrat
77
What assumptions are made when using the capture mark release recapture method?
- The time allowed for random mixing is enough
- Changes in population size are negligible
- Movement of the organisms is restricted geographically
- There’s even dispersing of organisms within the study area
- The mark does not hinder the movement of the organism, or make them conspicuous to predators
- There are few if any deaths and births within the population
- The mark or label is not lost or rubbed off during the investigation
78
State the disadvantages of capture mark release recapture method
- It is only reliable when the organisms range of movement is restricted and defined
- Animals often moving groups, whose members recognize and avoid mixing with any other group
- Loss of marked individuals reduces accuracy
- The mark may psychologically or physically disturb the organism
79
Define biological control methods (BCM)
This is the eating or weakening of a pest species or weeds using other organisms called control agents
eg beetles to eat water hyacinth, fish in ponds to eat mosquito larvae, cats to eat rats
80
What are the advantages of using BCM?
- It is very specific to the target organism.
- No danger of environmental pollution.
- Control agent may become useful food material to other organisms.
- No extinction of target organism but marinated in the carrying capacity.
- No pest resistance or resurgence.
- Biomagnification and bioaccumulation do not occur.
81
What are the problems of using BCM?
- Pests are not fully eliminated.
- Control agents can change prey.
- Pest replacement may occur.
- Waste pollution in aquatic habitats.
- Need to control the agent in case of population explosion.
82
Define chemical method of population control
This involves the use of chemical substances by humans to eradicate harmful organisms
83
Define the term pest
A person is an organism that competes for resources with humans
84
What is a pesticide?
Poisonous chemicals which kill pests
85
What are the properties of an ideal pesticide?
- Should be biodegradable
- Should be specific
- Should not accumulate
- Should have effective control of the pest under field growing conditions
- Should be easy to apply at the correct dosage
86
What are the dangers of using pesticides?
- Pest resistance
- Pest replacement
- Pest resurgence
- Bioaccumulation and biomagnification
-Accidental misuse result in death of humans and domestic animals
87
Define bioaccumulation
This refers to the gradual build up of toxic chemicals in the tissues of an organism overtime.
88
Define biomagnification
This is the process by which the concentration of a substance gradually increases in higher trophic levels of a food chain
89
What is pest resurgence?
The population increase of a pest species after it has temporary been suppressed
90
What does the competitive exclusion principle state? (Gause’s principal)
No two species can occupy the same ecological, niche and competing for the same limited resources at the same time in the same area
91
What does the competitive exclusion principle state? (Gause’s principle)
No two species can occupy the same ecological niche at the same time in the same area
92
Define competition
This is a relationship, whereby two individuals of the same species or different species struggle to obtain resources, which are in limited supply
93
Define intraspecific competition
This is the competition between members of the same species for the same resources.
94
Define interspecific competition
This is the competition between members of two or more different species for limited resources.
95
What is competitive advantage?
This is the ability of one organism to have a higher chance of getting resources over another organism it is competing with
96
Give examples of competitive advantages in animals
- Faster growth
- Faster reproduction.
- Smaller in size.
- Production of toxins.
- Better structural features.
- Feeding on competitors
- More resistant to toxins.
- Efficient food absorption.
- Faster metabolism.
97
Give examples of competitive advantages in plants
- Broad leaves
- Taller
- Deep roots
- Higher amount of chlorophyll
- Many roots
- Structural adaptations, such as thorns
98
What are the competitive advantages of P. Aurelia?
- High rate of reproduction
- High growth rate
- Good nutrient absorptive capacity
- Being small, it requires less food and can survive when food is scarce
- Survivorship, long lifespan
99
What is resource partitioning?
This is where two different species co-exist, and share the same resources and both species survive
100
What are the modes of resource partitioning?
- Different feeding times
- Vertical separation
- Horizontal separation
- Migration
101
What is the importance of competition?
- Population control
- Evolution
- Spacing out (maximum resource utilization)
102
Why is competition harmful to both species?
Neither one can attain their maximum size
103
What is predation?
Feeding relationship, where one organism of a given species, hunts, kills and feeds on another of a different species
104
What is a predator?
This is an organism that hunts kills and feeds on organisms of another species
105
What is prey?
This is the live organism which is fed on by the predator
106
How are predators suited for capturing prey?
- They have keen eyesight for locating prey
- Some are able to camouflage
- Nocturnal predators have highly developed sense of detecting sound made by prey
- Some snakes have glands that secrete poison
- Webs spinning spiders use their silky webs to catch small sized insects
- Some have soft pads to go undetected as they walk to prey
- Some have , stinging cells which paralyzed prey
- They have long and sharp canines
- Will developed limbs
- Some hunt in packs
- Developed sense of smell
- Their eyes are close together for focusing
- Long, sharp claws
- Some lay traps
107
What is the significance of predation?
- Reduces competition
- It is a biological control method
- Determines the distribution and abundance of prey
108
How are prey species suited to avoid predation?
- Ability to run swim or fly faster
- Possession of highly developed sense of smell
- Protective shells
- Coiling
- Puffing up
- Living in large groups
- Mimicking
- Camouflage
- Having spines or thorns
- Small sized
- Huge
- High-voltage shock
- Eyes are far apart
- Secrete, poisonous repellent, substances
- Group defense
109
What is symbiosis?
Any type of a close and long-term biological interaction between two different biological organisms
110
Define parasitism
This is a symbiotic relationship between two organisms in which one (parasite) obtains all its nutrients from the body of another (host), the host suffers harm
111
What is a parasite?
An organism, depending on a host organism for food and shelter and in turn causes harm to it
112
What are the adaptations of parasites to the mode of life?
- Some are able to respire, anaerobically
- Hooks to attach to host
- Suckers to obtain nutrients from the host
- Some secrete inhibitor substances that prevent them from being digested
- High reproduction rates
- Inflicts minimal harm to the host
- Degeneration of unwanted organs
- Penetrative devices
- Use of vectors
- Having a dormant resistant stage
113
What are the benefits of predator-prey relationships?
- Maintains both populations at carrying capacity as they regulate their number interpedently
- They eliminate the weak and aged predators and preys thereby maintaining a healthy populations
- They allow evolution of better adapted predators and preys via natural selection
- They allow nutrient cycling and energy flow
- These relationships avail resources to both predators and preys by maintaining carrying capacity
114
What is mutualism?
This is an interspecific association in which both organisms benefit
115
Give examples of mutualistic organisms
- Legumes and Rhizobium bacteria
- Cellulase secreting bacteria in the gut of ruminants
- Algae and fungi (Lichens)
116
Define commensalism
This is an association between organisms of different species in which one benefits while the other neither benefits nor is harmed
Eg cow and egret
117
What is co-evolution?
This is a long-term evolutionary adjustment of two or more groups of organisms that facilitate those organisms living with one another
118
What is antibiosis?
This is the secretion of chemical substances by organisms which may be repellent to members of the same species or different species
119
Define intraspecific antibiosis
This is secretion by organisms of chemical substances into the surrounding, that may be repellent to members of the same species
Male rabbits secrete pheromones from their salivary glands used to mark territory.
120
Define interspecific antibiosis
This is the secretion by organisms of chemical substances into the surrounding, that may be repellent to members of different species
The fungus penicillium, secretes antibiotics, that prevent bacterial growth
121
What is pollution?
This is the addition of harmful or toxic substances, or energy in large amounts that cause permanent environmental damage
122
What is biodegradation?
The breakdown of complex chemical pollutants by biological means
123
What is greenhouse effect?
This is a condition when greenhouse gases like carbon dioxide, methane and others allow cause trapping of heat in the atmosphere.
124
What is global warming?
This is the observed average global temperature rise as a result of enhanced natural greenhouse effect
125
What is eutrophication?
A natural process during which water bodies are enriched with nutrients due to excessive discharge of salts in sewage and fertilizers.
126
What are the effects of eutrophication?
- Species diversity decreases and the dominant biota change
- Plant, algal and animal biomass increases leading to algal bloom
- Turbidity of water increases
- Sedimentation increase
- Dissolved oxygen in water decreases/Anoxic conditions may develop
- Stratification
